Fd Chem. Toxic. Vol. 22, No. 1 pp. 83-92, 1984 0278-6915/84 $3.00+0.00 Printed in Great Britain Pergamon Press Ltd

Information Section

A STRANGE LOOK AT RED DYES

The use of short-term in vitro tests to screen for chemical carcinogens has been advocated by many authorities. The now classical Ames test and others designed to identify bacterial and mammalian mu- tagens exploit the correlation between mutagenesis and carcinogenesis and have attained a degree of respectability. However, many test systems relying on correlations between other biochemical events and carcinogenicity have been proposed. For the most part, these alternative tests have failed to stand up to extensive investigation. Thus, the induction of aryl hydrocarbon hydroxylase (AHH) activity has been shown to correlate with the carcinogenicity of aro- matic hydrocarbons, but probably has little relevance to the carcinogenicity of other classes of chemicals (Gelboin, Physiol. Rev. 1980, 60, 1107). Similarly, although guanylate cyclase activity has been shown to be induced in a variety of tissues by some carcino- gens, including N-nitrosamines (DeRubertis & Cra- ven, Science, N.Y. 1976, 193, 897), methyl nitro- sourea (Vesely et al. Cancer Res. 1977, 37, 28) and hydrazine (Vesely & Levey, Biochem. biophys. Res. Commun. 1977, 74, 780), the range of compounds investigated and the tissue specificity of the response is too limited to allow any conclusions to be drawn as to the relevance of this enzyme to carcinogenicity.

Rochat & Vesely (ibid 1983, 111, 409) have now examined the effect of five red food dyes on these two systems (AHH and guanylate cyclase) and have at- tempted to relate the findings to what is known----or has been suspected--about the long-term effects of these dyes. Of the materials investigated, negative results have been obtained in carcinogenicity studies on new coccine (Ponceau 4R; BIBRA unpublished data, 1981), erythrosine (FD & C Red No. 3; Hansen et al. Fd Cosmet. ToxicoL 1973, 11, 527, and others) and carmine of cochineal (BIBRA unpublished data, 1981). Amaranth (FD & C Red No. 2) was at one time suspected of being a weak carcinogen on the basis of two studies (Andrianova, Vop. Pitan. 1970, 29(5), 61; Gordon & Taylor, unpublished FDA study, 1975, cited by JECFA, Tech. Rep. Set. Wld Hlth Org. 1978, 631, 18 and WHO Fd Add. Ser. No. 13 (1978), p. 4). However, both of these studies were judged by JECFA to be unacceptable and amaranth has recently been shown to be non-carcinogenic in

another long-term rat study (BIBRA unpublished data, 1982).

Rochet & Vesely (loc. cit.) investigated in vitro the effects of a range of concentrations (0.001-0.1/~M) of the five test dyes on the activities of AHH and guanylate cyclase from rat liver. Amaranth enhanced the activities of both enzymes approximately twofold at the highest concentration, but had no effect at the lower levels. Cochineal caused a similar maximal stimulation of both enzyme activities at the higher concentration, and also produced a roughly twofold stimulation of AHH activity at 0.01/tM and of gua- nylate cyclase activity at both 0.001 and 0.01 pM. Carmine enhanced AHH activity by approximately 50~o and guanylate cyclase by 100~ at all concen- trations. No effects were seen with new coccine or with erythrosine. The authors also showed that the enhancing effect of amaranth, cochineal and carmine was independent of the Mn ÷ ÷ content of the medium for guanylate cyclase activation. They conclude from this study that cochineal's enhancement of these enzymes was PoSsibly due to its carmine content (since new coccine, another cochineal pigment, had no such effect) and that "at the cellular level there is no biochemical evidence that red No. 3 is a carcino- gen". However, the relevance of these results to the assessment of the safety of amaranth and other food dyes is not clear. Neither enzyme system has been shown to be generally useful for the prediction of carcinogenicity, and no dyes of undisputed carcino- genicity were included in the study. The mechanism by which guanylate cyclase activity is induced by xenobiotics is not known, nor is it known whether AHH induction is a consequence of guanylate cyclase activation or unrelated to it. It is known, however, that the hepatic reduction of amaranth, although probably mediated by cytochrome P-448/P-450, is not related to AHH activity (Fujita & Peisach, Phar- macologist 1976, 18, 206). Furthermore, as it is known that very little ingested amaranth is absorbed to reach the liver intact (Takeda et al. Nippon Nog- eikagaku Kaishi 1981, 55(2), 125; BIBRA un- published data, 1982) the changes in hepatic enzyme activities brought about by exposure to unchanged dye seem at best only remotely relevant to the assessment (by implication) of the carcinogenicity of this food colouring.

MECHANISM OF ORTHOPHENYLPHENOL TOXICITY

The broad-spectrum antimicrobial ortho- phenylphenol (OPP) and its sodium salt (OPP-Na) can be used to protect edible crops against fungal contamination. An ADI for OPP of 1 mg/kg body weight was established by WHO (1969 Evaluations o f

Some Pesticide Residues in Food, FAO/PL: 1969/M/17/1, p. 185, FAO/WHO, Rome, 1970) mainly on the basis of short-term and long-term studies in rats.

However, more recently Hiraga & Fujii (Fd Cos-

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