Subcellular localization and properties of cytochrome P-450 and UDP glucuronosyltransferase in the rainbow trout kidney

Abstract

Rainbow trout kidney was subfractionated by differential centrifugation to obtain preparations suitable for the study of xenobiotic metabolizing enzymes and to ascertain the distribution of these activities in the cell. The cytochrome P-450-dependent monooxygenase, NADPH-cytochrome c reductase, and UDP glucuronosyltransferase, which are enzymes important in the biotransformation of xenobiotics, were enriched in the microsomal fraction. Another xenobiotic-metabolizing enzyme, epoxide hydrolase, was enriched in the mitochondrial and microsomal fractions almost to the same extent. Cytochrome P-450-dependent monooxygenase and UDP glucuronosyltransferase activities were characterized in the trout kidney microsomes. The cytochrome P-450 deethylation of 7-ethoxycoumarin and 7-ethoxyresorufin as well as the glucuronidation of p-nitrophenol in the kidney were found to proceed at rates comparable to those occurring in the liver. The difference spectrum of the complex between carbon monooxide and reduced trout kidney microsomes showed a peak at 448.5 nm. Addition of 7-ethoxycoumarin to kidney microsomes produced an absorbance change in difference spectrum similar to the substrate binding spectrum found in rainbow trout liver and rat liver microsomes.