[Inhibition of serotonin-induced platelet aggregation by endothelins]

Endothelins are a family of three peptides that act as local hormones in all mammalian species. They were found to inhibit rabbit and dog platelet aggregation in vivo, whereas no effect was observed in vitro. In order to investigate the possible interaction between endothelins and human platelet serotonergic receptors, their effect on the platelet aggregation, induced by serotonin, was studied. Endothelin-1, -2 and -3 had a dual action for platelet aggregation induced by serotonin. When added simultaneously to serotonin endothelins aggregatory response to this amine was potentiated. On the contrary, preincubation of platelet suspension with endothelins resulted in a concentration-dependent inhibition of serotonin-promoted platelet response. Moreover, endothelin-1 inhibited serotonergic amplification of epinephrine-induced aggregation of platelets. It is proposed that endothelins bind to the platelet membrane and interact with serotonergic receptors and/or G proteins. The diverse effect of eodothelins on serotonin-induced aggregation of platelets may be due to stimulation of protein kinase C.