Metabolism of 5(6)-expoxyeicosatrienoic acid by ram seminal vesicles. Formation of novel prostaglandin E1 metabolites.

5(6)-Epoxy-8,11,14-eicosatrienoic acid was incubated with microsomes or ram seminal vesicles in the presence of glutathione (1 mM) for 2 min at 37 degrees C. Following extractive isolation on octadecasilane silica, the products were purified on straight-phase HPLC and separated into three major polar metabolites, which all showed maximal ultraviolet absorbance at 278 nm after treatment with alkali. The least-polar of the three metabolites was identified by capillary column gas chromatography-mass spectrometry as 5(6)- epoxyprostaglandin E1 and the structure was confirmed by comparison with authentic material. The most-polar metabolite was identified as 5,6- dihydroxyprostaglandin E1, while the metabolite of medium polarity was identified as its delta 5-lactone. When glutathione was omitted, 5-hydroxyprostaglandin I 1 alpha and 5-hydroxyprostaglandin I 1 beta were previously identified as the two major metabolites. These results indicate that the postulated epoxyprostaglandin endoperoxide intermediates, 5(6)- epoxyprostaglandin G1 and 5(6)- epoxyprostaglandin H1, might be substrates for the endoperoxide E isomerase enzyme, since this enzyme requires glutathione as a cofactor.