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P-NITROPHENOL METABOLISM BY JAPANESE MEDAKA (ORYZIAS LATIPES) LIVER MICROSOMES AND S-9 FRACTION: ADDITIONAL EVIDENCE FOR THE EXISTENCE OF A CYP2E1-LIKE ISOFORM IN TELEOSTS
Citation:
Geter, D. R., A. Brouwer, W. E. Hawkins, AND J W. Fournie. P-NITROPHENOL METABOLISM BY JAPANESE MEDAKA (ORYZIAS LATIPES) LIVER MICROSOMES AND S-9 FRACTION: ADDITIONAL EVIDENCE FOR THE EXISTENCE OF A CYP2E1-LIKE ISOFORM IN TELEOSTS. Presented at American Fisheries Society Fish Health Section 2000 Annual Meeting, Pensacola Beach, FL, 6-8 September 2000.
Description:
Liver microsomes and S-9 fraction of Japanese medaka (Oryzias latipes) metabolized the CYP2E1 specific substrate, p-nitrophenol (PNP), to a single hydroxylated product, 4-nitrocatechol. The use of liver S-9 fraction proved to be a viable alternative to liver microsomes and allowed data to be collected from individual fish. PNP metabolism was linearly related to microsomal and S-9 protein and dependent on NADPH. Maximal activity was found at 27?C, but was detectable at all temperatures tested. Baseline PNP-hydroxylation activity was greater in male than female medaka (27.74 ? 1.66 and 14.04 ? 2.52 pmol/mg/min, respectively) and fasting for 96-hours was able to increase baseline activity two fold in both sexes. Exposure to the CYP2E1 specific inducers, ethanol (5ppt) and acetone (6ppt) for 96-hours increased PNP-hydroxylation activity two fold in non-fasted male medaka. The results of this study provide additional evidence for the presence of a CYP2E1-like isoform in teleost liver and form the basis to evaluate the use of the medaka as a fish model for studying this enzyme and its role in chemical carcinogenesis.