LIVER-MICROSOMES FROM THE YELLOW AAT SNAKE (ELAPHE OBSOLETA) AND AMERICAN BULLFROG (RANA-CATESBEIANA) OXIDIZE POLYUNSATURATED FATTY-ACIDS BY NADPH-DEPENDENT HYDROXYLATION AND EPOXIDATION

Polyunsaturated fatty acids (PUFAs) can be oxygenated by mammalian hep atic P450s to a series of metabolites. The most prominent of these are formed by omega- and (omega-1)-hydroxylation, epoxidation of the doub le bonds or bisallylic hydroxylation. The object of the present invest igation was to determine whether similar oxygenations are catalyzed by liver microsomes of the yellow rat snake (Elaphe obsoleta) and the Am erican bullfrog (Rana catesbeiana). Liver microsomes were incubated wi th [1-C-14]-labeled arachidonic (AA), eicosapentaenoic (EPA), and lino leic acids (LA) in the presence or absence of 1 mM NADPH, and the majo r metabolites were analyzed by reverse-phase and straight-phase high p erformance liquid chromatography and capillary gas chromatography-mass spectroscopy. No metabolites were produced in the absence of NADPH. P rofiles of metabolites were different depending on the organism and th e acclimation state. In all incubations, EPA was the most effective su bstrate utilized and LA the least effective. The major products from E PA were 19-HEPE, 13-HEPE, and 20-HEPE from cold-acclimated (5 degrees C), warm-acclimated (22 degrees C) frogs, and snakes (22 degrees C), r espectively. In contrast, 20-HETE production from AA was greater than 19-HETE in all three. Cold-acclimated frog liver microsomes produced s ignificantly more of all metabolites when compared With microsomes fro m warm-acclimated frogs. We conclude that amphibian and snake liver ca n catalyze epoxidation and hydroxylation of PUFAs and that products ar e species-specific and acclimation-state dependent. (C) 1998 Wiley-Lis s, Inc.