Effects of feeding ethyl-dihomo-gamma-linolenate on rabbit renomedullary lipid composition and prostaglandin production in vitro.

Feeding the ethyl ester of dihomo-gamma-linolenic acid for 25 days to rabbits resulted in increased PGE1 (20 to 30-fold) and PGE2 (1.5-fold) output by a hormone responsive, in vitro, renal papilla preparation. The relative amount of PGE1 increased from less than 5% of PGE2 in controls to 25-35% of PGE2 in the papillae of 20 : 3 omega 6-supplemented animals. During the study renomedullary tri glycerides in the 20 : 3 omega 6-supplemented animals increased 2.8-fold compared to animals fed an equal amount of a control fatty acid mixture, and in addition to a marked enrichment in 20 : 3 omega 6, also contained increased proportions of 20 : 4 omega 6 and longer chain polyenes. The increase in triglyceride content found in the renal medulla was not seen in the renal cortex or liver. There was no increase in renomedullary phospholipid content during the study, and phopholipids of treated animals contained increased proportions of 20 : 3 omega 6 and 20 : 4 omega 6, but not longer chain polyenes. The results indicate that enriching the prostaglandin precursor pool by feeding 20 : 3 omega 6 can alter the type and amount of prostaglandin released by the renal papilla, at least in vitro. Also, the selective changes in amount and long chain polyene content of renomedullary triglycerides during the study suggest some special functions for this lipid class in prostaglandin precursor metabolism.