Initial characterization of drug-metabolizing systems in the liver of the Northern pike, Esox lucius.

NADPH-cytochrome c reductase, cytochrome -450, benzo[a]pyrene mono-oxygenase, epoxide hydratase, and glutathione S-transferase activities in the liver of the Northern pike (Esox lucius) have been measured and partially characterized. The level of these systems in pike liver is between 13.2 and 133% of the corresponding levels in rat liver, with the exception of glutathione S-transferase, whose specific activity in the high-speed supernatant fraction of pike liver is 305% of that in rat liver. In addition, pike liver contains about 23% of the mammalian level of reduced glutathione. Drug-metabolizing systems in pike liver are distributed in essentially the same manner in subfractions as the corresponding systems in the liver of mammals. Benzo[a]pyrene mono-oxygenase and epoxide hydratase activities display the expected pH maxima of 7.5 and 9.5, respectively, and have temperature maxima of 37 degrees and 47 degrees C, respectively. NADPH-cytochrome c reductase and glutathione S-transferase activities are relatively independent of temperature. Intraperitoneal treatment of Northern pike with methylcholanthrene induces the benzo[a]pyrene mono-oxygenase activity of liver microsomes 33-fold.