Xenobiotic metabolizing enzyme activity in the liver and kidney of the brown bullhead (Ictalurus nebulosus)

Activities of aryl hydrocarbon hydroxylase (AHH), epoxide hydrase (EH), glutathione-S-transferase (GST) and UDP-glucuronyl transferase (UDPGT) were easily detected in brown bullhead (Ictalurus nebulosus) liver. AHH (substrate-³H-benzo(a)pyrene). GST (substrate-l-chloro-2,4-dinitrobenzene) and EH (substrate-³H-benzo(a)pyrene-4,5-oxide) activities in kidney were 4, 60 and 183%, respectively, of the corresponding values in liver. UDPGT (substrate -p-nitrophenol) was not detected in the kidney of control or 3-methylcholanthrene (3-MC)-treated fish. Treatment of bullhead with 3-MC enhanced the activity of AHH in liver and kidney nearly 14- and 33-fold, respectively, with little or no effect on EH or GST activity at the time point tested. The types of benzo(a)pyrene (BP) metabolites formed by liver and kidney microsomes were qualitatively similar, but there were considerable differences in the patterns of the metabolites produced by the microsomes from the two tissues. The liver microsomes from control fish converted a substantially greater proportion of BP to quinones than did the kidney microsomes.