Effects of sodium selenite on in vitro interactions between platelets and endothelial cells

Selenium is an essential component of glutathione peroxidase enzymes, which protect cells against peroxidation and control concentrations of intracell ular proxides. Since selenium deficiency is associated with an increased in cidence of arterial thrombosis, we studied the effect of selenium on in vit ro interactions between platelets and endothelial cells. Platelets from nor mal volunteers on a diet with (PLTSe+) or without (PLTSe-) selenium supplem entation and human umbilical vein endothelial cells cultured in medium alon e (ECSe-) or supplemented with Se (ECSe+) were used. The effect of in vivo administration or in vitro supplementation of selenium on platelet function was investigated in an aggregometry model designed for studying the intera ctions between platelets and endothelial cells using ADP and arachidonic ac id as agonists. We observed that: (1) selenium-dependent glutathione peroxi dase enzyme activity increased in both PLTSe+ and ECSe+, being about fivefo ld higher in the former; (2) platelet aggregation was inhibited by Se+ cell s; (3) Se+ cells released less thromboxane B-2 (PLTSe+) and more 6-keto-pro staglandin F-1 alpha (ECSe+) than Se- cells; (4) when ECSe+ were treated wi th acetylsalicylic acid, the inhibitory effect of selenium on platelet aggr egation disappeared; (5) the concentration of nitric oxide metabolites in S e+ culture media did not differ from that in Se- media. We suggest that an antithrombotic effect on the interactions between platelets and endothelial cells can be induced by stimulating glutathione peroxidase enzymes with se lenium via a mechanism that is blocked by acetylsalicylic acid and is appar ently unrelated to the biosynthesis of nitric oxide metabolites.