Oleic acid-induced Ca2+ mobilization in human platelets: is oleic acid an intracellular messenger?
The purpose of this study was to explore the effect of oleic acid (OA) on intracellular Ca2+ mobilization in human platelets. When applied extracellularly, OA produced a concentration dependent rise in cytosolic [Ca2+] ([Ca2+]cyt) when extracellular [Ca2+] (Ca2+]ext) was zero (presence of EGTA), suggesting that OA caused an intracellular release of Ca2+. Intracellular Ca2+ release was directly proportional to entry of OA into platelets and OA entry was indirectly proportional to [Ca2+]ext. In permeabilized platelets, OA caused the release of 45Ca2+ from ATP dependent intracellular stores. Finally, our results show that thrombin stimulated the release of [3H]OA from platelet phospholipids. The saturated fatty acids stearic and palmitic acid did not stimulate an increase in [Ca2+]cyt under these conditions, but the unsaturated fatty acid, linolenic acid produced effects similar to those of OA, suggesting specificity among fatty acids for effects on [Ca2+]cyt. Taken together, our 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 stimulates Ca2+ release from intracellular stores. These results support the hypothesis that OA may serve as an intracellular messenger in human platelets.
Siafaka-Kapadai
A
A
Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284, USA.
Hanahan
D J
DJ
Javors
M A
MA
D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000097:blood*; D002855:Chromatography, Thin Layer; D004075:Diglycerides / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008854:Microscopy, Electron; D019301:Oleic Acid / Q000378:metabolism / Q000494:pharmacology*; D010539:Permeability; D010743:Phospholipids / Q000378:metabolism; D012503:Saponins / Q000494:pharmacology; D015290:Second Messenger Systems / Q000502:physiology*; D013917:Thrombin / Q000494:pharmacology; D014280:Triglycerides
D004075:Diglycerides; D005227:Fatty Acids; D010743:Phospholipids; D012503:Saponins; D014280:Triglycerides; D019301:Oleic Acid; D007770:L-Lactate Dehydrogenase; D013917:Thrombin; D002118:Calcium; D016257:Fura-2