Induction of mixed function oxidases by petroleum in the American eel, Anguilla rostrata

American eels, Anguilla rostrata, were exposed to crude oil by ingestion of a 10, 100, or 500 microliters/kg fish dose per day for five days. Depuration was followed for an additional twelve days. All oil doses caused an induction of hepatic microsomal enzymes, maximally by three days of exposure. Benzo(a)pyrene hydroxylase (BaPH) showed a dose related response, with greater induction at 100 microliters/kg than at the other doses. The highest dose was hepatotoxic. Cytochrome P-450 induction was dose independent, and remained induced maximally for the entire experimental period, in contrast to BaPH which declined in activity. Reaction optimum for BaPH was at pH 7.5 and 27 degrees C. A study of tissue distribution showed the liver to account for nearly all BaPH activity. A significant increase in the protein content of the hepatic postmitochondrial fraction of oil-exposed fish was also observed.