Comparative effects of indole and aminoacetonitrile derivatives on dimethylnitrosamine-demethylase and aryl hydrocarbon hydroxylase activities.

The effect of in vivo administration of indole and five 3-indolyl derivatives including L-tryptophan, as well as of aminoacetonitrile and 3 of its derivatives, were studied on the carcinogen-metabolizing hepatic mixed-function oxidases dimethylnitrosamine (DMN)-demethylase I and II and aryl hydrocarbon hydroxylase (AHH). Indole, 3-indolylmethanol, 3-indolyl-acetonitrile, 3-indolylacetone and L-tryptophan induce AHH activity from 3- to 6-fold of the control level, whereas beta-3-indolylethanol has no effect; the latter compound produces a 21% decrease of the endoplasmic reticulum content in the tissue. Only L-tryptophan induces DMN-demethylase I and only L-tryptophan and 3-indolylmethanol induce DMN-demethylase II, representing a doubling of enzyme activity in all 3 instances. Aminoacetonitrile is a potent repressor of DMN-demethylase I. Substitutions on the amino group bring about strong decrease or abolishment of mixed-function oxidase repressor activity; thus, iminodiacetonitrile has only about 1/5th the repressor activity of the parent compound, whereas nitrilotriacetonitrile and dimethylaminoacetonitrile appear to be inactive. Aminoacetonitrile and its derivatives studied have no effect on DMN-demethylase II and AHH activities. The mixed-function oxidase-modifying effects of the indole compounds and of aminoacetonitrile and its derivatives illustrate the potential complexity of effects of dietary constituents on the carcinogenic responses.

Enhancement of toxicity and enzyme-repressing activity of p-dioxane by chlorination: stereoselective effects.

The acute toxicity of p-dioxane may be enhanced up to 1000-fold by chlorination of the compound. The effect was stereoselective. Of the stereoisomers tested, tetrachloro-p-dioxane, isomer I (2r, 3t, 5t, 6c) was over 80 times more toxic than isomer II (2r, 3c, 5t, 6t). The latter compound was also a potent repressor of hepatic dimethylnitrosamine-demethylase I (DMN-d) and aryl hydrocarbon hydroxylase (AHH).