Effects of carcinogens on hormonal regulation of gene expression in primary cultures of adult rat hepatocytes.

The report utilizes knowledge of the regulation of tyrosine aminotransferase (TAT) activity in rat liver as the basis for the development of a model system for investigating the effects of carcinogens on gene expression. A protocol utilizing primary monolayer cultures of adult rat hepatocytes was employed. The addition of dexamethasone resulted in a 5-fold induction of TAT activity; adding glucagon along with dexamethasone gave a 12-fold induction. The chemicals tested for possible effects on TAT induction were aflatoxins B1, B2, G1, G2, 2-acetylaminofluorene, 2-aminofluorene, 7,12-dimethylbenz[a]anthracene, 3-methylcholanthrene, and benzo[a]pyrene. Carcinogens inhibited the induction of TAT activity by dexamethasone alone or with glucagon in a dose dependent manner, and in general there was a correlation between inhibition of TAT induction and in vivo carcinogenic potency. In addition to the inhibition of TAT induction, the carcinogens similarly inhibited RNA synthesis and to a lesser extent, protein synthesis. The inhibition of these biochemical activities did not appear to be due to cell death.