Source of arachidonic acid for prostaglandin synthesis in Madin-Darby canine kidney cells

Abstract

Madin-Darby canine kidney cells deacylate arachidonic acid from cellular phospholipids in response to stimulation with 12-O-tetradecanoyl-phorbol-13-acetate and convert the free arachidonic acid to prostaglandins. We have used this system to determine which phospholipids serve as donors of the free arachidonic acid. The cells were labeled with [3H]arachidonic acid and [14C]palmitic acid which were preferentially incorporated into phosphatidylethanolamine and phosphatidylcholine, respectively. 12-O-Tetradecanoyl-phorbol-13-acetate stimulation caused a marked deacylation of arachidonic acid from phospholipids including 1-alk-1'-enyl-2-acyl-sn-glycero-3-phosphoethanolamine; phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, and phosphatidylcholine were also donors of arachidonate. A smaller percentage of the [14C]palmitic acid was lost from phospholipids after stimulation and indicates that the stimulated deacylation of phospholipids is preferential for [3H]arachidonic acid compared to [14C]palmitic acid. Analysis of the cellular phospholipid acyl composition demonstrated that 12-O-tetradecanoyl-phorbol-13-acetate stimulation caused a marked decrease in the content of arachidonic acid and an increase in saturated and monounsaturated fatty acids. These findings suggest that the phospholipids which serve as arachidonic acid donors are rapidly reacylated with more saturated fatty acids.