OLEIC ACID-INDUCED CA2- IS OLEIC-ACID AN INTRACELLULAR MESSENGER( MOBILIZATION IN HUMAN PLATELETS )

The purpose of this study was to explore the effect of oleic acid (OA) on intracellular Ca2+ mobilization in human platelets. When applied e xtracellularly, OA produced a concentration dependent rise in cytosoli c [Ca2+] ([Ca2+](cyt)) when extracellular [Ca2+] ([Ca2+](ext)) was zer o (presence of EGTA), suggesting that OA caused an intracellular relea se of Ca2+. Intracellular Ca2+ release was directly proportional to en try of OA into platelets and OA entry was indirectly proportional to [ Ca2+](ext). In permeabilized platelets, OA caused the release of Ca-45 (2+) from ATP dependent intracellular stores. Finally, our results sho w that thrombin stimulated the release of [H-3]OA from platelet phosph olipids. The saturated fatty acids stearic and palmitic acid did not s timulate an increase in [Ca2+](cyt) under these conditions, but the un saturated fatty acid, linolenic acid produced effects similar to those of OA, suggesting specificity among fatty acids for effects on [Ca2+] (cyt). Taken together, out experiments suggest that OA which has been incorporated into platelet phospholipids was released into the cytosol by thrombin stimulation. Our experiments also show that OA stimulated Ca2+ release from intracellular stores. These results support the hyp othesis that OA may serve as an intracellular messenger in human plate lets. Copyright (C) 1997 Elsevier Science B. V.