Formation of PGI3 in the rat during dietary fish oil supplementation.

Conflicting results exist in the literature on the conversion of eicosapentaenoic acid (EPA) to trienoic prostaglandins and its influence on the formation of dienoic prostaglandins from arachidonic acid (AA). Tissues from animals fed fish oils produce little, if any, trienoic prostaglandins and reduced amounts of dienoic ones. Excretion of the major urinary metabolite of PGI2 is not reduced in humans taking fish oil, however, and substantial amounts of one derived from PGI3 have been found, by GC/MS. We have addressed this possible species difference by examining the urine of rats fed fish oil for 2.3 dinor-6-keto-PGF1 alpha and its delta 17 analog, formed from PGI2 and PGI3, respectively, and compared them with rats fed corn oil. Fatty acid differences in erythrocyte and aortic lipids were also determined. Rats fed fish oil do make PGI3 from eicosapentaenoic acid in vivo and do not suppress their production of PGI2, despite having more EPA than AA in aortic lipids.