Influence of prostaglandin E-1 on the endothelium platelet interaction

Background and aim: Following the discovery of prostaglandin E-1 (PGE(1)) i ts inhibitory, effect on platelet activity has been the rationale for its t herapeutic application - initially intra-arterial, later intravenous with n o loss of effect but reduced side effects. The aim of the present study was to compare the value of the inhibitory effect on platelet function with th at of other pharmacological effects of PGE(1). Methods and results: We analysed the findings of all our own studies on the effects of PGE(1) on platelets and endothelium and also those reported in the literature up to 1998. In contrast to the in vitro effect of PGE(1) on platelet function, an ex vi vo effect on platelet function is hardly demonstrable. In vivo, however; PG E(1) significantly prolongs platelet survival, reflecting an improved plate let/vascular wall interaction. This observation, together with a reduction in the number of circulating endothelial cells, as well as the inhibition o f adhesion molecule expression and vascular thrombogenicity under PGE(1) in dicate that the vessel wall surface (endothelium) is of particular signific ance in the regulation of haemostasis in vivo. This is also supported by th e observation that although, under conditions of simulated flow, PGE(1) sig nificantly reduces adhesion of pre-exposed platelets to the vessel wall in vitro, the same effect in vivo requires PGE(1) pretreatment of the vessel w alls; here, it would seem that the influence of platelet function is of onl y secondary importance. The optimal therapeutic regimens established on the basis of thrombogenicity and survival time of radiolabelled autologous pla telets are identical to those currently in clinical use. Conclusion: The analysis has clearly shown that the vasculoprotective effec t of PGE(1) in vivo is of far greater importance than its effect oil platel ets.