title: Microsomal and cytosolic epoxide hydrolase and glutathione S-transferase activities in the gill, liver, and kidney of the rainbow trout, Salmo gairdneri. Baseline levels and optimization of assay conditions.
abstract: Microsomal and cytosolic epoxide hydrolase (mEH and cEH respectively) and glutathione S-transferase (GST) activities were measured in the liver, kidney, and gills of rainbow trout. Assays were optimized for time, pH, and temperature, using trans-stilbene oxide (TSO) and cis-stilbene oxide (CSO) as substrates for cEH and mEH, respectively. Optimal pH values for mEH, cEH, and GST were similar to mammalian values (i.e. 8.5, 7.5, and 9). Temperature optima differed between tissues and cell fractions. Specific activity of cEH-TSO was 3-14 times greater than mEH-CSO for all three tissues, and 8-60 times greater on a tissue weight basis. Liver and, to a lesser extent, kidney mEH were active against benzo[a]pyrene 4,5-oxide, whereas gill mEH was not active against this substrate. Liver cytosolic GST was active against CSO and 1-chloro-2,4-dinitrobenzene (CDNB) but not TSO, whereas gill and kidney cytosolic GST were active only against CDNB. Liver and kidney microsomal GST were active against CDNB, but no activity was found in gill microsomes. The results are discussed in relation to possible endogenous substrates and uninduced xenobiotic metabolizing capacities of different trout tissues.
authors.affiliation: Department of Medicine, School of Veterinary Medicine, University of California, Davis, 95616.
authors.forename: D J
authors.initials: DJ
authors.lastname: Laurén
authors.forename: P P
authors.initials: PP
authors.lastname: Halarnkar
authors.forename: B D
authors.initials: BD
authors.lastname: Hammcock
authors.forename: D E
authors.initials: DE
authors.lastname: Hinton
mesh_terms: D000818:Animals; D003600:Cytosol / Q000201:enzymology; D004851:Epoxide Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005880:Gills / Q000201:enzymology; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000201:enzymology; D008862:Microsomes, Liver / Q000201:enzymology; D012487:Salmonidae / Q000378:metabolism*; D013267:Stilbenes / Q000378:metabolism; D013696:Temperature; D014337:Trout / Q000378:metabolism*
chemical_list: D013267:Stilbenes; D005982:Glutathione Transferase; D004851:Epoxide Hydrolases; C025906:stilbene oxide