Selectivity of food colours for different organic acid transport systems in rat renal cortex

Seventeen food colours were tested as inhibitors of the simultaneous uptake of labelled o-iodohippurate and iodipamide into slices of rat renal cortex. The results have been interpreted in terms of inhibition of two different aniontransport systems: the hippurate of H-system and the liver-like L-system. No clearcut relation was found between inhibition ability and system specificity on the one hand and moleculr weight or structure on the other. However, most disulphonic azo dyes and quinoline yellow show an L-system affinity while tri-and tetra-sulphonic azo dyes, triarylmethanes and erytrosine show very little predilection for either of the two systems.

Food, drug, and cosmetic dyes: biological effects related to lipid solubility

Food, drug, and cosmetic dyes of the xanthane type (analogs of fluorescein) were applied to isolated molluscan ganglia and changes in the electrophysiological properties of identified neurons were monitored. The synthetic coloring agents increased the resting membrane potential and conductance of the neurons in a dose-dependent manner by increasing the potassium permeability of the membrane relative to that of other ions. The relative activity of these anionic dyes was highly correlated with their lipid solubility. The structure-activity study of the effects of the dyes on molluscan neurophysiology provides a basis for estimating the toxicity and brain uptake of the dyes in vertebrates, and predicting their effects on metabolism and blood clotting.

Mutagenicity of the food colour brown FK and constituents in Salmonella typhimurium

The food colour Brown FK (EEC Serial No. 124) is a mixture of p-sulphophenylazo derivatives of m-toluylenediamine and m-phenylenediamine and is used in the UK for colouring kippers. Brown FK and its constituents were assayed for mutagenicity in Salmonella typhimurium TA 1535, TA 1537 and TA 1538. Samples of Brown FK from three manufacturers were mutagenic in TA 1538 (framshift mutant) when activated by a rat-liver supernatant fraction. Mutagenicity was linearly dose-dependent in the range of 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 Brown FK, 2,4-diamino-5-(p-sulphophenylazo)-toluene (I) and 1,3-diamino-4-(p-sulphophenylazo)benzend (II), each present at about 18% in the complete colour, were mutagenic in TA 1538. Mutagenicity was linearly dose-related in the range 0--1 mumol/plate, with slopes of 0.35 mutants/nmol for compound I and 1.5 mutants/nmol for compound II. This activity was dependent on metabolic activation. Four other major constituents, (di- and tri-substituted diamines) were inactive, as was sulphanilic acid, the major excretion product of Brown FK. The mutagenicity of Brown FK could be largely accounted for by the combined effects of compounds I and II. Earlier studies showed that compounds I and II were responsible for the acute myotoxic effects seen when Brown FK was given per os to rats and pigs. Azoreductive fission of I and II to reactive triamines by gut microflora was thought to be the main metabolic pathway by which Brown FK produced its myotoxic effects, and it is proposed that the mutagenic effects of Brown FK are probably mediated by a similar mechanism.

Mutagenesis in cultured human diploid cells. IV. Induction of 8-azaguanine resistant mutations by phloxine, a mutagenic red dye

Disodium 9-(3',4',5',6'-tetrachloro-o-carboxyphenyl)-6-hydroxy-2,4,5,7-tetrabromo-3-isoxanthone (phloxine), a red dye used as a food additive, was tested for its activity to induce 8-azaguanine (8AG) resistant mutations in cultured human embryonic cells. Phloxine had a severe cytotoxic effect on the cells at concentrations of 1 to 10 mug/ml. At concentrations of more than 30 mug/ml of phloxine no further decrease in cell survival was found. This cytotoxic effect of phloxine was not dependent on the duration of treatment. After treatment with phloxine for 2 h division of cells in normal medium was inhibited for 120 h. When cells were treated with phloxine at various concentrations for 2 h, cultured in normal medium for 48 h, and then selected with 30 mug/ml of 8AG, an increase in the induced mutation frequency was found. This increase in mutation frequency was dependent on the concentration of phloxine used as a mutagen and treatment with 100 mug/ml of phloxine increased the frequency to six times that in untreated cultures.