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Inhibition by aflatoxin B1 of hydrocortisone induction of rat liver tryptophan pyrrolase and tyrosine transaminase

1968; Elsevier BV; Volume: 128; Issue: 2 Linguagem: Inglês

10.1016/0003-9861(68)90058-1

1096-0384

Gerald N. Wogan, Marvin A. Friedman,

Carcinogens and Genotoxicity Assessment

Aflatoxin B1 inhibited hydrocortisone induction of rat liver tryptophan pyrrolase and tyrosine transaminase when administered simultaneously with or within 2 hours after the inducer. Thereafter, the induction process was insensitive to the toxin. These responses were qualitatively similar to those caused by actinomycin D and suggest that inhibition caused by the two compounds may be effected through similar mechanisms. Injection of aflatoxin B1 in single doses prior to hydrocortisone administration resulted in inhibition of tryptophan pyrrolase inducibility which persisted for at least 10 days at toxic dose levels (3–5 mg/kg). Under the same conditions, tryptophan-induced increases in enzyme activity were not affected by the toxin. These effects are thought to be associated with the hepatotoxicity of the compound.