Brown FK is prepared by coupling diazotised sulfanilic acid with
    a mixture of m-phenylenediamine and tolylene-2,4-diamine. The
    product contains 6 major coloured components, viz.:

    I    1,3-diamino-4-(4'-sulfophenylazo)-benzene

    II   2,4-diamino-5-(4'-sulfophenylazo)-toluene

    III  1,3-diamino-4,6-bis(4'-sulfophenylazo)-benzene

    IV   1,3-diamino-2,4-bis(4'-sulfophenylazo)-benzene

    V    2,4-diamino-3,5-bis(4'-sulfophenylazo)-toluene

    VI   1,3-diamino-2,4,6-tris(4'-sulfophenylazo)-benzene

         Brown FK was evaluated at the twenty-first meeting of the
    Committee (Annex 1, reference 44), at which time it was noted that, in
    long-term studies in mice, Brown FK produced hepatic nodules and
    tissue pigmentation. Some of the metabolites are cardiotoxic. The
    reproduction/teratogenicity studies that had been performed were
    inadequate and no ADI could be established. A toxicology monograph was

         Since the previous evaluation, additional data have become
    available and are summarized and discussed in the following monograph.
    The previously-published monograph has been expanded and is reproduced
    in its entirety below.


    Biochemical aspects

    Absorption, distribution, excretion, and bio-transformation

         After an i.p. dose to a rat of 1.5 g/kg b.w. the extremities
    became orange in 60 minutes, and the animal sluggish. After 24 hours
    the animal was normal but the urine was deep orange-yellow (Goldblatt
    & Frodsham, 1952).

         On incubation with the contents of rat ileum and caecum, Brown FK
    and its coloured components underwent azo-reductive fission with
    formation of sulfanilic acid, a phenazine-like material (P), and ill-
    defined products that could be separated chromatographically. Brown FK
    also underwent azo-reductive fission when incubated with rat-liver

    homogenate, but P was not detected among the products. Oral
    administration of Brown FK to rats, guinea-pigs, rabbits, and pigs
    resulted in the excretion of sulfanilic acid in urine and faeces;
    P was detectable in trace amounts in the faeces, but was mainly
    present in caecal contents, predominantly during the first 6 hours
    after dosing. A "blue material" was excreted in urine. On i.p.
    administration to rats, Brown FK initially gave rise to brown
    colouring in bile; later, sulfanilic acid and the "blue material"
    appeared in the urine. P was not found in faeces or in caecal contents
    (Fore & Walker, 1967; Fore, et al., 1967).

         As formed in vitro from Brown FK, P was found to consist of
    2 main components, P1 and P2, which were identified as
    1,4,7-triaminophenazine and 8-methyl-1,4,7-triaminophenazine,
    respectively. The "blue material" was tentatively identified as an
    indamine, which is an intermediate in the formation of P from the
    amines produced by azo-reduction of the monoazo components of Brown
    FK. Since 1,2,4-triaminobenzene oxidizes spontaneously in air to give
    the indamine and P1, it is possible that the "blue material" and P
    arose from aerial oxidation of the amines formed by azo-reduction of
    components of Brown FK; this oxidation may have occurred during the
    extraction and separation of caecal contents and faeces, or in the
    urine after excretion (Fore et al., 1967; Walker, 1968).

         In view of the complexity of Brown FK and the final mixture of
    metabolites, investigations have been conducted on individual
    components. The metabolism of 1,3-diamino-4-(4'-sulfophenylazo)-
    benzene and 2,4-diamino-5-(4'-sulfophenylazo)-toluene were found to be
    qualitatively similar, a proportion being excreted unchanged, but the
    bulk reductively cleaved to sulfanilic acid and the corresponding
    amine (the latter being acetylated before excretion). The authors
    expected that the metabolism of other Brown FK components would not be
    fundamentally different, and that the primary metabolic reactions
    would be products of cleavage of the azo linkages (Howes, 1969; Munday
    & Kirby, 1969).

         Incubation of 4 individual components of Brown FK (2 mono-,
    1 bis-, and 1 tris-azo-component) with rat caecal contents confirmed
    that azo-reduction occurred in all cases (Walker, 1968).

         A summary of the products of azo reduction of the 6 major
    components of Brown FK is shown below:



         The metabolism of 1,3-diamino-4-(4'-sulfophenylazo)-benzene
    (component I) in the rat is summarized below (Howes, 1969; Munday &
    Kirby, 1969):


         Preliminary examination of urine from rats fed component II
    showed the presence of sulfanilic acid and small quantities of
    unchanged dye. Examination of an extract of the urine revealed the
    presence of 5-acetamido-2,4-diaminotoluene (the major metabolite),
    2,5-diacetamido-4-aminotoluene, 2,4-diacetamido-5-amino-toluene, and
    4,5-diacetamido-2-amino-toluene. Unchanged dye was identified in
    faecal extracts; no other dye-derived compounds were detected.

         The metabolism of 2,4-diamino-5-(4'-sulfophenylazo)-toluene
    (component II) in the rat is summarized below (Munday, 1969):


         An attempt was made to determine whether 1,3-diamino-4
    (4'-sulfophenylazo)-benzene (component I) is reductively cleaved in
    humans, as in rats. Reduction of the closely-related compound,
    prontosil rubrum, has been shown to occur in human subjects (Fuller,


         Administration of component I to human subjects led to no
    detectable unchanged dye in the urine and no appreciable urinary
    excretion of sulfanilic acid. It can be inferred from these results
    that component I is not absorbed from the intestine as such, but no
    information was given on the possible reduction of this compound
    in vivo, since it was shown that orally-administered sulfanilic acid
    is not absorbed in man. Sulfanilic acid, if formed from the dye, would
    therefore be excreted in the faeces; the experimental confirmation of
    this was not provided and these studies were not pursued further
    (Jenkins & Favell, 1971).

         1,2,4-triaminobenzene and 2,4,5-triaminotoluene have been shown
    to uncouple oxidative phosphorylation in vitro, interfering with ATP
    production in the muscle cell, and to ionic imbalance with cell death
    (Munday, 1971).

    Toxicological studies

    Special studies on carcinogenicity


         A carcinogenicity study on Brown FK was performed in CD rats with
    an in utero exposure phase. Animals of the F0 generation (390 of
    each sex) were allocated to 6 groups; 2 groups were untreated
    (controls), 3 groups received diets containing Brown FK at constant

    dietary concentrations of 160, 530, or 2630 ppm (expressed as
    "coloured components of Brown FK"), and 1 group received sodium
    chloride at an amount equivalent to the amount of sodium salts
    received by the highest Brown FK-dose group. The animals received
    these diets for 14 days prior to pairing and during pregnancy and
    lactation. At weaning (28-31 days post-partum), 60 male and 60 female
    animals of the F1 generation were selected from each dose group for
    the long-term study. Thereafter, the Brown FK concentration in the
    diet of the treated groups was adjusted to maintain constant dosages
    of Brown FK of 15, 50, or 250 mg/kg b.w./day (expressed in terms of
    coloured components); 2 groups served as untreated controls and one
    group (salt control) received sodium chloride equivalent to the amount
    of sodium salts received by the highest Brown FK-dose group. The study
    was terminated when mortality in any treatment group exceeded 75%,
    males and females being considered separately. Accordingly, terminal
    sacrifices were initiated 105 weeks and 110 weeks after weaning of
    males and females, respectively.

         During the carcinogenicity study, animals were inspected twice
    daily and palpated once weekly. Moribund animals were sacrificed and a
    complete necropsy was performed on these rats and on those which died
    during the course of the study. Ophthalmoscopic examinations were
    performed on 20 males and 20 females from 1 control group and the 
    top-dose group after 26, 52, 77, and 102 weeks; the same animals were
    examined on all 4 occasions and animals that died or were killed were
    not replaced. Urinalysis was carried out on 10 rats of each sex from
    each dose group after 103 weeks (males) or 105 weeks (females).
    Haematological examinations and clinical chemistry investigations were
    performed on 10 males and 10 females of each group after 104 weeks
    (males) or 106 weeks (females).

         Rats killed in extremis or at termination were subjected to a
    complete necropsy and the following organ weights were recorded:
    adrenals, brain, heart, kidneys, liver, ovaries/testes, pituitary,
    spleen, and thyroid. Histopathological examinations were performed on
    rats of both sexes from 1 control group, the top-dose group, the salt-
    control group, and on any organs from the other groups that displayed
    gross abnormalities. The tissues examined histopathologically
    included; adrenals, aortic arch, bone, bone marrow, brain (3 levels),
    caecum, colon, diaphragm, duodenum, epididymides, eyes, heart, ileum,
    jejunum, kidneys, liver (2 lobes), lungs, lymph nodes (cervical and
    mesenteric), mammary gland, nasal cavities, oesophagus, ovaries,
    pancreas, parathyroids, pituitary, prostate, salivary gland, sciatic
    nerve, seminal vesicles, skeletal muscle, skin, spinal cord
    (2 levels), spleen, stomach, testes, thymus, thyroid, tongue, trachea,
    urinary bladder, and uterus (including cervix).

         In the reproductive phase of the study, there were no treatment-
    related effects on general condition, food intake, body-weight gain,
    mating performance, conception rate, or length of gestation. Litter
    size, growth, and viability of the offspring were unaffected by
    treatment with Brown FK. In the carcinogenicity phase, body-weight
    gains in rats of either sex receiving Brown FK at a dose of 250 mg/kg
    b.w./day were lower than body-weight gains in the combined control
    groups; at termination the weight decrements were 14 and 10% for males
    and females, respectively. Food consumption was not affected by
    treatment, but water intakes of rats receiving 250 mg/kg b.w./day of
    Brown FK and of rats in the salt-control groups were greater than of
    untreated controls. No treatment-related effects were seen in
    ophthalmic or haematological examinations, nor in urine composition.
    Clinical chemistry investigations revealed higher creatine
    phosphokinase, lactate dehydrogenase, and hydroxybutyrate
    dehydrogenase activities in female rats of the top-dose group compared
    with untreated controls, but not compared with salt controls.
    Isocitrate dehydrogenase activities were higher among rats of both
    sexes receiving the highest dose of Brown FK than among controls; no
    effects were seen at the lower doses. In males, but not females, of
    the highest-dose group, plasma albumin and T4 concentrations were
    significantly elevated.

         A total of 252 male and 236 female animals died or were killed
    in extremis during the treatment period, but the mortality
    distribution was unrelated to treatment. A total of 277 males and 308
    females had palpable swellings during the treatment period but the
    distribution, frequency, and time of onset were unaffected by

         No treatment-related differences were observed in absolute or
    relative organ weights at necropsy, but the incidence of dark thyroid
    glands among animals of the top-dose group was higher than controls.
    On histopathological examination, rats exposed to the highest-dose
    level of Brown FK exhibited deposition of brown pigment at particular
    sites (heart, skeletal muscle, diaphragm, tongue, thyroid, caecum, and
    hepatic kupffer cells) but this was not associated with any tissue
    reaction and was not observed at dose levels of 15 or 50 mg/kg
    b.w./day of Brown FK. Treatment with Brown FK was not associated with
    enhancement of neoplasia at any site (there was a reduced incidence of
    tumours in animals of the top-dose group compared with controls).

         Chronic myocarditis occurred with high frequency in all groups,
    but the incidence and severity were no greater in treated animals than
    in controls. In females, but not males, exposure to the highest-dose
    level of Brown FK was associated with an increased incidence of pelvic
    nephrocalcinosis; this effect was not seen at lower-dose levels. There
    was an increase in cystic distension of the follicles of the thyroid
    in high-dose group females, where the lesion was seen in 40.7% of the
    animals, compared with 17.2% of the controls; there was no evidence of
    any effect at lower-dose levels.

         The authors concluded that Brown FK was not carcinogenic in rats
    under the conditions of the experiment and that the no-effect level
    was 50 mg/kg b.w./day (Tesh et al., 1980; Amyes et al., 1983; Roe,

    Special studies on mutagenicity

         Brown FK and its constituents were assayed for mutagenicity in
    Salmonella typhimurium TA1535, TA1537, and TA1538 when activated by
    a rat-liver supernatant fraction. Mutagenicity was linearly dose-
    dependent in the range 0-3 mg/plate, with activities ranging from 22
    to 50 times the spontaneous mutation frequency. One sample of Brown FK
    was mutagenic in the absence of metabolic activation, producing a
    16-fold increase in mutation at 4 mg/plate. Two major constituents
    of Broom FK, 2,4-diamino-5-(4'-sulfophenylazo)toluene (II) and
    1,3-diamino-4-(4'-sulfophenylazo)benzene (I), each present at about
    18% in the complete colour, were mutagenic in TA1538. Mutagenicity was
    linearly dose-related in the range 0-1 Ámol/plate, with slopes of
    1.5 mutants/nmol for compound I and 0.35 mutants/nmol for compound II.
    This activity was dependent on metabolic activation. Four other major
    constituents were inactive, as was sulfanilic acid, the major
    excretion product. The combined effects of compounds I and II could
    largely account for the mutagenicity of Brown FK (Venitt & Bushell,

    Special studies on reproduction


         A multigeneration reproduction study was carried out in rats in
    which groups of 24 of each sex were given Brown FK in the diet at a
    level of 300 ppm for 5 weeks post-weaning, then at 600 ppm for 3
    successive generations; control animals received stock diet. After
    weaning, the parental animals and offspring not selected for breeding
    in the succeeding generation were culled. Haematological and clinical
    chemistry studies were performed on 10 animals of each sex from the
    parents and offspring, and autopsies carried out. Selected organ
    weights were recorded at autopsy on the parents and on 30 animals of
    each sex per group from the offspring. Histopathology was performed on
    F3 weanlings, 10 animals of each sex per group.

         Fertility, number of young per litter, birth weights, growth
    rates, gestation indices, viability indices, and lactation indices
    were unaffected by treatment; there was no indication of increased
    mortality in utero. No treatment-related lesions were observed at
    autopsy nor on histopathological examination of F3 weanlings. In
    clinical observations (plasma biochemistry/haematology) and in organ
    weights, occasional statistically-significant differences were seen;

    these were not consistent and, in the absence of pathological lesions,
    were not considered to be of toxicological significance. Under the
    conditions of the study, Brown FK was without adverse effect on
    reproductive performance (Wilson et al., 1983b).

    Special studies on teratogenicity


         Groups of 35 virgin female Wistar rats were mated with virgin
    males and were fed diets containing 0, 0.03, 0.15, or 0.6% Brown FK
    from day 0 to day 19 post coitus. Additional groups received 0.6%
    sodium chloride (salt control) or aspirin (250 mg/kg b.w./day).
    Successful pregnancies were achieved in 32-35 animals per dose group.
    Five pregnant animals per group were allowed to litter normally and
    then raise their offspring to weaning. The remaining animals were
    sacrificed on day 21 of gestation and the foetuses removed by
    Caesarian section. Two-thirds of the foetuses were examined for gross
    soft-tissue abnormalities, then cleared and stained with Alizarin red
    for examination for skeletal defects. The remaining one-third were
    examined for soft tissue defects using Wilson's technique. No
    treatment-related abnormalities were observed in any of the groups
    receiving Brown FK, and this was confirmed in the groups which were
    examined at weaning. Aspirin used as a positive control induced
    teratological defects in foetuses and in young reared to 21 days
    post partum (Unilever, 1978).

    Special studies on pigment deposition

         After feeding Brown FK to rats and mice, pigment was found in
    heart, skeletal muscle, tongue, diaphragm, thyroids, brain, liver,
    kidneys, spleen, lungs, pancreas, bladder, testes, ovary, uterus,
    skin, stomach, duodenum, ileum, brown fat, and bone marrow. In
    addition, a pigment has been detected in the plasma of rats.

         Staining tests commonly used to identify lipofuscin were negative
    with the exception of the test for metachromasia with toluidine blue.
    The tests applied were as follows;


                                Usual response of   Response of Brown
                                known lipofuscin    FK-induced pigment

    Test for iron                  negative            negative

    Sudan fat stains               positive            negative

    Reduction of ferric salts      positive            negative

    Reduction of ammoniacal
      silver salts                 positive            negative

    Basophilic properties          positive            negative

    Periodic acid - schiff
      reaction                     positive            negative

    Acid fastness                  acid fast           negative

    Toluidine blue at pH3          stains              greenish

         Two further histochemical tests clearly differentiated between
    lipofuscin and the Brown FK-induced pigment:

    -    Potassium permanganate/oxalic acid bleached lipofuscin, but not
         the Brown FK-induced pigment.

    -    Sodium dithionite bleached both lipofuscin and the Brown FK-
         induced pigment. However, after rinsing and allowing to stand in
         air, the Brown FK-induced pigment reappeared; lipofuscin was
         permanently bleached.

         The Brown FK-induced pigment does not fluoresce in ultra-violet
    light. On the other hand, all samples of lipofuscin which Brown FK
    have been examined were fluorescent. Pigment has been found in the
    thyroid, brown fat, and bone marrow; these tissues have not been
    recorded as being sites for lipofuscin deposition. Furthermore, a
    coloured substance has been demonstrated in the plasma, which has
    never been found with lipofuscin.

         The speed at which the Brown FK-induced pigment is deposited is
    uncharacteristic of lipofuscin information. In acute studies, pigment
    has been seen in the intestinal wall and villi within 24 hours of
    feeding the dye, and in the kidney after 5 days. Pigment masses
    produced in macrophages either in vivo after the intraperitoneal

    injection of Brown FK into mice, or in vitro, when Brown FK was
    incorporated in the macrophage culture medium, appeared identical.
    Tests for lipofuscin proved negative; the pigment in the macrophages
    closely resembled that seen in macrophages in stained sections of
    tissues from rats and mice fed Brown FK.

         Electron microscope studies have identified differences in
    morphology between lipofuscin and the Brown FK-induced pigment. In
    aged rats and mice fed Brown FK, conjugate forms were observed in
    which induced pigment and control lysosomal material appeared in the
    same membrane-limited body (Hope, 1971).

         It is likely that a component of Brown FK is oxidized within the
    cell to 1,4,7-triaminophenazine:


         This would explain the behaviour of the pigment with sodium
    dithionite, which reduces the phenazine ring to the 5,10-dihydro
    derivative, which is probably colourless. After exposure to air
    re-oxidation would occur. Thus, the pigment may not represent evidence
    of sub-lethal cell damage, but is, instead, an insoluble oxidation
    product of a dye metabolite.

         1,2,4-triaminobenzene was very rapidly oxidized to
    1,4,7-triaminophenazine by a mitochondrial suspension; no
    phenazine derivatives were detected with triaminotoluene under
    the same circumstances (Kirby, 1968b).

         1,4,7-triaminophenazine is a brown, water-insoluble, material
    which is very readily formed from 1,2,4-triaminobenzene (Muller,

    Special studies on pigment in tissues

         Histological tests were applied to sections of hearts and livers
    from female rats fed Brown FK at doses of 0, 15, 50, or 250 mg/kg
    b.w./day for 106-108 weeks. These tissues were obtained from animals
    used in the carcinogenicity study (see above). In addition, several
    tissues taken from weanling rats discarded at the end of the in
    utero phase were screened to determine if any pigment was present at
    the start of the long-term study due to transplacental transfer of
    Broom FK or through exposure during lactation/creep feeding.

         Rats fed Brown FK for over 2 years at a dose-level of
    250 mg/kg b.w./day displayed substantial pigment deposition in the
    heart and liver, but no effects were seen in these organs at the lower
    dose-levels. Brown FK-associated pigment was not found in tissues from
    weanling rats exposed to Brown FK in utero. The no-effect level for
    pigment accumulation in the long-term study was 50 mg/kg b.w./day.
    Differential tests showed that the pigment was not formalin pigment or
    haemosiderin, but tests aimed at differentiating between lipofuscin
    and Brown FK-induced pigment gave inconclusive results (Wilson et
    al., 1983a).

    Special studies on components I and II of Brown FK


         Groups of 3 male and 3 female C57Bl mice were fed diets
    containing 0, 0.5, or 1.0% of the "azobenzene" or "azotoluene"
    components of Brown FK (components I & II, respectively) for 6 weeks.
    With both components, the thyroids were dark and the intestines and
    squamous portions of the stomach were stained salmon-pink. Heart
    lesions were seen in all mice fed 1% component II, but not in those
    given component I. More pigment was seen in mice fed component I, less
    in those fed component II (Kirby, 1968a).


         Groups of 3 male and 3 female Colworth-Wistar rats were fed
    component I or component II at dietary levels of 0, 0.5, or 1% for 6
    weeks. The thyroids of rats receiving component I were dark and the
    hearts, muscles, and brains were stained. However, the intestines were
    stained only slightly. Pale hearts and meningeal haemorrhage were seen
    with component II, otherwise pigmentation was as with component I.
    One-sixth of the rats treated with component I and four-fifths of the
    rats treated with component II had heart lesions. More pigment was
    seen histologically in component I-treated rats, less in component
    II-treated animals (Kirkby, 1968a).

    Special studies on amine metabolites of Brown FK

         Amines derived from Brown FK and from its 2 myotoxic components,
    components I and II, were injected i.v. into rats in single doses of
    3.13-25 mg/kg. The mixture of amines from Brown FK was also injected
    into mice in the same range of doses. Cardiac and muscular lesions
    were produced by the amines in both species. These amines are
    biological degradation products in the intestine. The finding that
    orally-administered Brown FK is myotoxic in rats but not in mice is
    probably due to differences in the intestinal flora in the 2 species
    (Walker et al., 1970).

         In another study, 1,2,4-triaminobenzene was given to groups of
    6-7 rats orally 5 days/week for 2 weeks at 50, 60, 75, or 100 mg/kg
    b.w./day. Six rats out of 7 receiving 100 mg/kg/day died after 3 doses
    with severe heart lesions; 7/11 on 75 mg/kg/day also died after 3
    doses. Heart pigmentation occurred after 5 days' treatment or longer.
    Animals on lower doses showed both extensive heart pigmentation and
    cardiac necrosis (Mulky et al., 1969).

         1,2,4,5-Tetraaminobenzene was given to groups of 6 rats orally 
    5 days/week for 2 weeks at 150 or 200 mg/kg b.w./day. 1,2,3,4-
    Tetraaminobenzene was given to groups of 6 rats orally 5 days/week for
    2 weeks at 125 or 166 mg/kg b.w./day. No frank heart lesions and only
    instances of diffuse increase in interstitial cells in the heart were
    observed. No heart or thyroid pigment deposition was observed (Mulky
    et al., 1969).

    Acute toxicity

    Species            Route             (mg/kg b.w.)                Reference

    Mouse              oral              >2,000 (with salt)          Grasso et al., 1968a
                       oral              1,100-2,250 (with salt)     Edwards & Wilson, 1966
                       oral              960-1,149 (no salt)         Edwards & Wilson, 1966
                       i.p.              1,500-2,000 (with salt)     Grasso et al., 1968a
                       i.p.              960-1,720 (with salt)       Edwards & Wilson, 1966
                       i.p.              840-880 (no salt)           Edwards & Wilson, 1966
    Rat                oral              >8,000 (with salt)          Grasso et al., 1968a
                       oral              900-1,910 (with salt)       Edwards & Wilson, 1966
                       oral              780-970 (no salt)           Edwards & Wilson, 1966
                       i.p.              750-1,150 (with salt)       Grasso et al., 1968a
                       i.p.              1,100-2,250 (with salt)     Edwards & Wilson, 1966
                       i.p.              960-1,150 (no salt)         Edwards & Wilson, 1966
    Guinea-pig         oral              3,000 (with salt)           Edwards & Wilson, 1966
                       oral              2,610 (no salt)             Edwards & Wilson, 1966
                       i.p.              900 (with salt)             Edwards & Wilson, 1966
                       i.p.              780 (with salt)             Edwards & Wilson, 1966
    Rabbit             oral              450-680 (with salt)         Edwards & Wilson, 1966
                       oral              390-590 (no salt)           Edwards & Wilson, 1966
    Chicken            oral              >10,000 (with salt)         Edwards & Wilson, 1966
                       oral              >8,700 (no salt)            Edwards & Wilson, 1966
         For all species, animals dying did so from within a few minutes
    to 96 hours. Many animals, after either oral or i.p. treatment, showed
    lack of coordination, hypersensitivity, and hyperactivity; convulsions
    usually preceded death (Edwards & Wilson, 1966).

         Meningeal congestion or haemorrhage was seen at post-mortem
    examination in rats and mice which died following both oral and i.p.
    treatment with 3.4 g/kg Brown FK as a 10% solution. This was the
    highest dose administered, and the condition may have been present to
    a lesser degree in animals treated with lower levels of Brown FK, but
    post-mortem identification of the lesion was made difficult by tissue
    colouration. The meningeal congestion/haemorrhage was probably caused
    by the sodium chloride in the dye solution, since this lesion is
    observed after administration of hypertonic solutions of sodium
    chloride to rats. In this instance, the lowest dose levels at which
    the meningeal lesion was observed were 6.0 g/kg of sodium chloride
    orally as a 10% solution and 4.0 g/kg i.p. as a 5% solution (Edwards &
    Wilson, 1966).

         Following oral intubation, external tissue colouration was
    apparent after several hours in rats and guinea-pigs. No colouration
    of the tissues was seen in rabbits and chickens. After i.p. injection,
    external tissue colouration was apparent and intense after a few
    minutes in rats and guinea-pigs. Colour was seen in the faeces of
    rats, mice, rabbits, and guinea-pigs up to 24 hours after oral
    treatment; it was also excreted in the urine of rats, mice, guinea-
    pigs, and rabbits within 15 minutes of either oral or i.p. treatment
    (Edwards & Wilson, 1966).

         Hearts from some rats and mice surviving for 21 days after
    treatment were examined histologically. Degenerative lesions were
    found in 15% of rats given orally 1-2.5 g/kg b.w. Brown FK, but not in
    rats given 3.37 g/kg b.w. Brown FK. The same lesions were found in 50%
    of mice given orally 0.9 g/kg b.w. Brown FK, but not when given 0.6,
    1.35, or 2.03 g/kg b.w. Brown FK. When given i.p., 25-60% of mice
    showed lesions at 0.75 and 1.03 g/kg b.w. Brown FK (Edwards & Wilson,

    Short-term studies


         Groups of 10 male or 10 female mice received the colour (either
    fresh or stored) at a level of 1 g/kg daily for 3 weeks. A significant
    reduction in body-weight gain was noted in the mice receiving the
    stored solution, but not in those receiving fresh solution. One male
    and 1 female receiving the fresh solution showed cardiac lesions
    (BIBRA, 1964).

         Daily oral or i.p. doses up to 2 g/kg or 1 g/kg, respectively,
    for 43 days to groups of 10 or 12 mice were well-tolerated (Grasso
    et al., 1968a).

         Groups of 10 male and 10 female mice (Colworth C57Bl strain,
    initially 6 weeks old) were fed for 90 days on a synthetic diet
    containing 0, 0.05, 0.075, 0.10, 0.25, 0.50, 0.75, 1.0, or 2.0% Brown
    FK (equivalent to 0, 0.025, 0.0375, 0.05, 0.125, 0.25, 0.375, 0.50, or
    1.0% Brown FK-coloured components) containing 51% dye component and
    47% salt. A further group of 20 mice were fed synthetic diet
    containing added 1.0% sodium chloride as a control for the additional
    dietary salt derived from the Brown FK. At the 0.125% dietary colour
    level, pigment deposition occurred in tissues. At 0.25% and above
    there was splenic enlargement, at 0.50% the liver and heart were
    enlarged, and at 1.0% there was reduced growth, poor food utilization,
    liver, spleen, heart, and testicular enlargement, and histological
    evidence of degenerative heart lesions. The thyroids, muscle,
    intestine and squamous part of the stomach were pigmented (Ashmole
    et al., 1958).


         Groups of animals received the colour at a level of 0.5 g Brown
    FK per kg b.w. for 3 weeks, orally or i.p. Twenty rats were dosed
    orally, of which 6 animals died after having been administered between
    5 and 11 doses. Post-mortem examination of rats dying during the test
    or killed at the end revealed general tissue-staining in 5 rats. Of 18
    hearts examined histologically, 8 showed degenerative lesions, and a
    brown pigment was observed in small amounts in 9 hearts after 3 weeks.

         In the multiple-dose i.p. test, 8 rats were treated and none died
    during the treatment period. General organ-staining was observed in
    all animals at post-mortem examination. Hearts from 7 rats were
    examined microscopically and degenerative lesions were found in 1
    heart and small amounts of pigment in 3 hearts after 3 weeks (Kirkby,

         No ill-effects were seen in 3 weanling rats given a 0.1% solution
    Brown FK for 28 days, the intake being equivalent to 15 mg/day
    (Goldblatt & Frodsham, 1952).

         Administration of 2 or 3 oral doses of 1 g Brown FK/kg b.w.
    to rats induced a myopathy in cardiac and skeletal muscles
    characterized by multiple vacuoles about 1-2 micrometers in diameter.
    Ultrastructurally, these were shown to consist of areas of
    fibrollolysis. Histochemically, the myopathy was accompanied by a
    moderate increase in acid phosphatase activity and by a loss of
    phosphorylase activity. Subsequently, complete lysis of the affected
    fibres ensued. In the heart, lysis was followed by macrophage invasion

    and fibroblastic proliferation, and in skeletal muscle by
    regeneration. The occurrence of lipofuscin in muscle fibres and in
    macrophages was scanty and erratic. When Brown FK was given in the
    diet at a level of 2%, fibrillolysis and an increase in the number and
    electron-density of lysosomes was observed ultrastructurally during
    weeks 2 to 3 of the test. These changes were accompanied by a marked
    elevation of histochemically-demonstrable acid phosphatase.
    Progressive deposition of lipofuscin was the principal pathological
    feature during weeks 3 to 12 (Grasso et al., 1968b).

         Daily oral doses of up to 2 g/kg Brown FK for 43 days to groups
    of 10 rats induced rapid loss of weight and death, with severe damage
    to cardiac and skeletal muscle, characterized by vacuolar myopathy and
    lipofuscin deposition. Of 3 pure components of Brown FK studied,
    component II, and to a lesser extent component I, produced similar,
    but not identical lesions to those induced by the parent colour after
    repeated oral doses of 0.5 g/kg. Ultrastructural studies confirmed an
    extensive loss of myofibrillar elements, and histochemical studies
    revealed a loss in the activity of mitochondrial enzymes. Similar i.p.
    injections in doses up to 1.0 g/kg for 43 days to groups of 10 or 12
    rats did not have any effect on the heart or skeletal muscle (Grasso
    et al., 1968b).

         Experiments were performed using groups of 10-12 rats receiving
    the colour at levels of 0.1 or 1 g/kg orally or 0.1, 0.25, or 1 g/kg
    i.p. daily for up to a maximum of 43 doses. A specific cardiac lesion
    was identified at the oral dose of 1 g/kg. There were large areas of
    myocardial necrosis and replacement by large mononuclears, with
    involvement of the sub-pericardial region and endocardium. Some
    myocardial cells had lost their stainable cytoplasm and appeared only
    as empty sheaths. When administered i.p., the colour produced little
    or no cardiac damage at any dose tested. At these high doses of 
    1 g/kg, most animals showed congestion, fatty change, or necrosis of 
    the liver with hydropic degeneration of the kidney. There was no 
    obvious splenomegaly. Daily doses of 100 mg/kg by stomach tube 
    produced 2 pericardial and 1 sub-pericardial lesions. In addition, 
    early hydroponic degeneration of the kidney was seen in 2 rats, with 
    1 of these animals also showing fatty change in the liver (BIBRA, 

         Administration of Brown FK (purity 80.0%) at dietary levels of 0,
    0.001, 0.01, 0.1, or 1.0% for 150 days showed no adverse effects on
    growth, food consumption, haematological indices, liver and kidney
    function, or organ weights. One male rat at the 1.0% level showed
    typical myocardial changes; other rats showed deposits of lipofuscin,
    especially in females. The no-effect level was 0.1% (Gaunt et al.,

         Groups of 12 male and 12 female rats (Colworth-Wistar strain,
    initially 3-4 weeks old) were fed for 112 days on a commercial stock
    diet containing 0, 0.05, 0.1, 0.5, 1.0, or 2.0% Brown FK (0, 0.025,
    0.05, 0.25, 0.5, or 1.0% Brown FK-coloured components) containing 51%
    dye component and 47% salt. A further group of 24 rats were fed the
    commercial stock diet containing added 1.0% sodium chloride as a
    control for the additional dietary salt derived from the Brown FK. In
    addition, to eliminate damage to the heart from cardiac puncture in
    any rat kept to 16 weeks, groups of 6 male and 6 female rats were fed
    6 weeks on powdered stock diet containing 0, 0.05, 0.5, or 2.0% Brown
    FK (0, 0.025, 0.25, or 1.0% Brown FK-coloured components). A group of
    12 rats also received 1.0% sodium chloride added to the basic diet.
    All these rats were used for biochemical tests during weeks 0-6 after
    which they were killed. At the 0.25% level tissue pigmentation
    appeared, at 0.5% liver enlargement occurred, and at the 1% level
    there was reduced growth, poor food utilization, enlargement of the
    liver, testes, and thyroid, histological evidence of degenerative
    heart lesions, increased urinary indican excretion, and elevation of
    SGOT. The intestine, squamous portion of the stomach, and the thyroid
    were stained. The no-effect level was 0.05% (Ashmole et al., 1966).


         Groups of female and male pigs were given doses of 0, 100, 250,
    or 500 mg Brown FK/kg/day for 24 weeks without adverse effects on
    growth, food consumption, haematological indices, liver and kidney
    function, or organ weights. Lipofuscin was widely distributed in
    animals of both sexes at all dose levels in one or more organs. The
    liver was particularly affected in that lipofuscan deposition was
    accompanied by increased lysosomal enzyme activity, which was more
    marked at the higher dose-levels. It was also seen in the heart in
    males, where it was associated with an increased acid phosphatase
    activity, and in the kidneys at the highest-dose level in females and
    at all levels in males. A no-effect level could not be determined in
    this study (Gaunt et al., 1968).

    Long-term studies


         Groups of 40 male and 40 female Colworth C57Bl mice were fed for
    80 weeks on a synthetic diet containing 0, 0.0125, 0.0375, 0.075,
    0.125, or 0.625% Brown FK-coloured components (the Brown FK used in
    this study contained 62.5% coloured components). Only at the 0.625%
    level was there reduced growth and food utilization and increased
    mortality among females. There were increased liver, kidney, spleen,
    brain, and testes weights, evidence of splenic haemopoisis, and
    increased myocardial fibrosis. Heart weights were increased at the
    0.125% level. Increased hepatic nodules were seen at 0.075% and higher

    levels and pigment deposition at 0.0375% and higher levels. At
    termination, after 80 weeks, the number of animals with nodules at the
    different dose levels was 26, 23, 27, 56, 42, and 64, respectively.
    Increased hepatic nodules were observed at 0.075% and higher levels.
    The number of mice with hepatocellular carcinoma were 3, 2, 0, 5, 6,
    and 2 at the various dose levels, respectively. Pigment deposition was
    observed at dose levels of 0.0375% and higher (Wilson et al., 1970).


         Groups of 32 male or 36 female Colworth-Wistar rats were fed for
    2 years on a synthetic diet containing 0, 0.01, 0.03, 0.06, 0.1, or
    0.5% Brown FK-coloured components (Brown FK used in this study
    contained 54.2% coloured components). Only at the 0.5% level was there
    increased splenic weight and hepatic granulomata. Pigment deposition
    was seen at dose levels of 0.06% and higher. The no-effect level for
    pigment deposition was 0.03%; it was 0.06% when based on toxicity
    evidence (Wilson et al., 1971).

    Observations in man

         No information available.


         The carcinogenicity study did not reveal any increase in the
    incidence of tumours, nor did the reproduction and teratogenicity
    studies show any adverse effects on reproductive function.

         The myopathy seen in rats given high doses of Brown FK in short-
    term studies affected all striated muscle, was accompanied by pigment
    deposition, and was dose-dependent with a high threshold. In the long-
    term/carcinogenicity study in rats, the observed myocarditis was not
    dose-related and there was no pigmentation in animals of the low-dose
    group nor controls. However, deficiencies in histopathological
    examination of tissues from the low- and intermediate-dose groups
    hindered the establishment of a no-effect level in this study.

         In earlier long-term studies, the no-effect level (with respect
    to pigment deposition) was 0.03% in the diet, equivalent to 15 mg/kg
    b.w./day, based on the coloured components of Brown FK.


    Level causing no toxicological effect

    Mouse:    0.0125% in the diet, equivalent to 19 mg/kg b.w./day.

    Rat:      0.03% in the diet, equivalent to 15 mg/kg b.w./day.

    Estimate of temporary acceptable daily intake for man

    0-0.075 mg/kg b.w. (based on colour components)

    Further work or information

    Required by 1986

         A complete histopathological examination of tissues from the low-
    and intermediate-dose groups in the long-term/carcinogenicity study in


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         span combined toxicity and oncogenicity study in rats pre-exposed
         in utero. 2. Toxicity and oncogenicity phase. Unpublished
         report No. 82/URL012/573 from Life Science Research, Essex, U.K.
         Submitted to WHO by Unilever Ltd.

    Ashmole, R.T., Campbell, P., Kirkby, W.W., & Wilson, R. (1966).
         Effects of feeding dietary Brown FK to rats for six and 16 weeks.
         Unpublished report from Unilever Research Laboratories. Submitted
         to WHO by Unilever Ltd.

    Ashmole, R.T., Kirkby, W.W., & Wilson, R. (1958). Thirteen week mouse
         feeding trial. Unpublished report from Unilever Research
         Laboratories. Submitted to WHO by Unilever Ltd.

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         Industrial Biological Research Association, Carshalton, Surrey,
         England. Submitted to WHO.

    Edwards, K.B. & Wilson, R. (1966). Acute toxicity of Brown FK in rats,
         mice, guinea-pigs, rabbits and chickens. Unpublished report from
         Unilever Research Laboratories.

    Fore, H. & Walker, R. (1967). Studies on Brown FK. I. Composition and
         synthesis of components. Fd. Cosmet. Toxicol., 5, 1-9.

    Fore, H., Walker, R., & Golberg, L. (1967). Studies on Brown FK. II.
         Degradative changes undergone in vitro and in vivo. Fd.
         Cosmet. Toxicol., 5, 459-473.

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         prontosil therapy? Lancet, 1, 194-198.

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         Brown FK. V. Short-term feeding studies in the rat and pig. Fd.
         Cosmet. Toxicol., 6, 301-312.

    Goldblatt & Frodsham (1952). Private communication from ICI
         (unpublished report).

    Grasso, P., Gaunt, I.F., Hall, D.E., Golberg, L., & Batstone, E.
         (1968a). Studies on Brown FK. III. Administration of high doses
         to rats and mice. Fd. Cosmet. Toxicol., 6, 1-11.

    Grasso, P., Muir, A., Golberg, L., & Batstone, E. (1968b). Cytopathic
         effects of Brown FK on cardiac and skeletal muscle in the rat.
         Fd. Cosmet. Toxicol., 6, 13-24.

    Hope, J. (1971). Ultrastructure of the pigment induced in various
         tissues of the rat by long-term feeding of the dye Brown FK.
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         to WHO by Unilever Ltd.

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         sulphophenylazo)benzene, a component of the dye Brown FK, in the
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         on pigment deposition and lesions in rats and mice. Unpublished
         report from Unilever Research Laboratories. Submitted to WHO by
         Unilever Ltd.

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         and mice fed Brown FK. Unpublished report from Unilever Research
         Laboratories. Submitted to WHO by Unilever Ltd.

    Mulky, M.J., Mundy, R., Ashmole, R.T., & Kirkby, W.W. (1969).
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         Research Laboratories. Submitted to WHO by Unilever Ltd.

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         toluene. Unpublished report from Unilever Research Laboratories.
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         Unpublished report from Unilever Research Laboratories. Submitted
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    See Also:
       Toxicological Abbreviations
       Brown FK (WHO Food Additives Series 12)
       BROWN FK (JECFA Evaluation)