Effect of essential polyunsaturated fatty acid modifications on prostaglandin production by MDCK canine kidney cells

Supplementation of growing MDCK canine kidney tubular epithelial cultures with linoleic acid produced a 3.6- to 4.9-fold increase in bradykinin-stimulated PGE2 release as measured by radioimmunoassay. Under these conditions the cell phospholipids contained 3.9- times more linoleic acid and 5.6-times more arachidonic acid, with the inositol, ethanolamine and choline phosphoglyceride fractions becoming enriched in arachidonic acid. By contrast, supplementation with arachidonic acid did not enhance bradykinin-stimulated PGE2 release even though the arachidonic acid content of the cell phospholipids was increased 8.8-fold. The distribution of radioactive prostaglandin products was unchanged by these fatty acid enrichments, with PGE2 accounting for 55 to 68% of the total output from [1-14C]arachidonic acid. Linoleic acid supplementation also produced a 2.5-fold increase in PGE2 formation stimulated by extracellular arachidonic acid, whereas supplementation during culture with arachidonic acid caused a 55 to 80% inhibition. This difference cannot be accounted for by changes in the ability of the cells to incorporate extracellular arachidonic acid. It is suggested that at least some of the effects of linoleate supplementation on prostaglandin production are due to the resulting enrichment of the intracellular phospholipid substate pools with arachidonic acid. In addition, it appears that prolonged exposure to arachidonic acid during culture has an overriding inhibitory effect on prostaglandin production even though the total cell lipids become highly enriched in arachidonate.