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2486. Io-dye-d
324
COLOURING MATTERS
order (linear) kinetics. Some 54--80 % of the administered dose was rapidly recovered in the bile, first-order kinetics again being followed at dose levels up to 20 ~moles, although at higher levels non-linear behaviour was observed. Application of digital and analogue curvefitting techniques suggested that at low doses amaranth uptake from blood by the liver was a first-order reaction, with amaranth remaining temporarily bound to liver tissues before first-order excretion into the bile. However, a small amount of reflux from liver to blood could not be excluded from the model.
2486. lo-dye-d Vought, R. L., Brown, F. A. & Wolff, J. (1972). Erythrosine: An adventitious source of iodide. J. din. Endocr. Metab. 34, 747. Studies of the possible biochemical repercussions following the breakdown of the food colouring, erythrosine, and the consequent release of iodine (I) have suggested no cause for concern at current levels of use. The present work was carried out to establish by the use of a refined radio-tracer method the extent to which iodide released from this important food and drug colouring may contribute to the dietary intake of I. The 127I and xalI levels in the thyroid, serum and urine were measured in groups of rats that had been fed on diets containing an erythrosine-coloured cereal for 3 or 5 wk and then given an intraperitoneal injection of 13~I as sodium iodide. Both ~a~I uptake by the thyroid and protein-bound radioactivity in the serum were reduced significantly in these rats, but there was an increase in serum radioactivity not bound to protein. The strongest evidence for erythrosine deiodination was, however, the marked rise in 127I levels in the urine and thyroid. When iodine-free [13q]erythrosine was administered to rats, 25-33 ~o was metabolized to iodide. Most of the free iodide appeared in the urifie, but it was also found to a small extent in the thyroids. [Extrapolation of the results of such work to man is difficult, since it is still not known how closely human metabolism of erythrosine resembles that in the rat, although some release of iodine from erythrosine has been demonstrated in man (Andersen et al. J. clin. Lab. Invest. 1964, 16, 249). We recently commented briefly on the possible significance of a high dietary intake of iodine (Cited in F.C.T. 1972, 10, 591).] 2487. Com0etitive attacks on azo dyes Du Plooy, Marianne & Dijkstra, J. (1971/72). Early stage in the metabolism of aminoazo dyes in the liver of rats. Chemico-Biol. Interactions 4, 163. Thorough examination of the metabolism of the azo dye, butter yellow (N,N-dimethylaminoazobenzene; DAB), has shown it to consist basically of three detoxication reactions (azo reduction, C-hydroxylation and N-demethylation) followed by steps that have been postulated to be involved in the carcinogenic action of the dye, namely N-hydroxylation and binding to cellular macromolecules (nucleic acids and proteins). The present paper examines the structure and function of the early DAB metabolites. In the livers of rats given 250 mg DAB/kg in a single dose by gastric intubation, TCAsoluble metabolites reached their maximum level 4 hr after treatment. These metabolites were fractionated into six components using high-voltage paper eleetrophoresis, the two
COLOURING MATTERS
order (linear) kinetics. Some 54--80 % of the administered dose was rapidly recovered in the bile, first-order kinetics again being followed at dose levels up to 20 ~moles, although at higher levels non-linear behaviour was observed. Application of digital and analogue curvefitting techniques suggested that at low doses amaranth uptake from blood by the liver was a first-order reaction, with amaranth remaining temporarily bound to liver tissues before first-order excretion into the bile. However, a small amount of reflux from liver to blood could not be excluded from the model.
2486. lo-dye-d Vought, R. L., Brown, F. A. & Wolff, J. (1972). Erythrosine: An adventitious source of iodide. J. din. Endocr. Metab. 34, 747. Studies of the possible biochemical repercussions following the breakdown of the food colouring, erythrosine, and the consequent release of iodine (I) have suggested no cause for concern at current levels of use. The present work was carried out to establish by the use of a refined radio-tracer method the extent to which iodide released from this important food and drug colouring may contribute to the dietary intake of I. The 127I and xalI levels in the thyroid, serum and urine were measured in groups of rats that had been fed on diets containing an erythrosine-coloured cereal for 3 or 5 wk and then given an intraperitoneal injection of 13~I as sodium iodide. Both ~a~I uptake by the thyroid and protein-bound radioactivity in the serum were reduced significantly in these rats, but there was an increase in serum radioactivity not bound to protein. The strongest evidence for erythrosine deiodination was, however, the marked rise in 127I levels in the urine and thyroid. When iodine-free [13q]erythrosine was administered to rats, 25-33 ~o was metabolized to iodide. Most of the free iodide appeared in the urifie, but it was also found to a small extent in the thyroids. [Extrapolation of the results of such work to man is difficult, since it is still not known how closely human metabolism of erythrosine resembles that in the rat, although some release of iodine from erythrosine has been demonstrated in man (Andersen et al. J. clin. Lab. Invest. 1964, 16, 249). We recently commented briefly on the possible significance of a high dietary intake of iodine (Cited in F.C.T. 1972, 10, 591).] 2487. Com0etitive attacks on azo dyes Du Plooy, Marianne & Dijkstra, J. (1971/72). Early stage in the metabolism of aminoazo dyes in the liver of rats. Chemico-Biol. Interactions 4, 163. Thorough examination of the metabolism of the azo dye, butter yellow (N,N-dimethylaminoazobenzene; DAB), has shown it to consist basically of three detoxication reactions (azo reduction, C-hydroxylation and N-demethylation) followed by steps that have been postulated to be involved in the carcinogenic action of the dye, namely N-hydroxylation and binding to cellular macromolecules (nucleic acids and proteins). The present paper examines the structure and function of the early DAB metabolites. In the livers of rats given 250 mg DAB/kg in a single dose by gastric intubation, TCAsoluble metabolites reached their maximum level 4 hr after treatment. These metabolites were fractionated into six components using high-voltage paper eleetrophoresis, the two