Differential induction of various carboxylesterases by certain polycyclic aromatic hydrocarbons in the rat

Hepatic and extrahepatic carboxylesterase (EC 3.1.1.1) activities were studied after the exposure of rats to polycyclic aromatic hydrocarbons. In dose- and time-dependent studies, the carcinogens benz[a]anthracene, benzo[a]pyrene and 3-methylcholanthrene moderately induced the hepatic cytosolic and kidney microsomal carboxylesterase activities, while the non-carcinogenic compounds anthracene, phenanthrene and chrysene had no effects on these enzyme activities. The hepatic microsomal and kidney cytosolic enzyme activities were not altered by the polycyclic aromatic hydrocarbons tested. Carboxylesterase activity in the postmitochondrial fraction of the intestinal mucosa decreased the serum enzyme activity slightly increased after the administration of the carcinogenic compounds. Although the in vitro hydrolysis of propanidid by hepatic cytosolic and kidney microsomal preparations was increased, the biological half-life of propanidid in vivo was not changed by 3-methylcholanthrene treatment.