Selenium compounds inhibit the biological activity of blood platelets

The action of inorganic forms of selenium (Se) on blood platelet aggregatio n, secretion and the arachidonate pathway in vitro was studied. It was show n that sodium selenite, after 30 min preincubation, inhibited platelet aggr egation induced by 0.1 U/ml of thrombin and by 10 mu M ADP (about 30% inhib ition of aggregation after pretreatment of platelets with 10(-4) M of Se). Contrary to sodium selenite, sodium selenate did not affect the platelet ag gregation induced by either agonist. Pretreatment of blood platelets with s odium selenite resulted in a statistically significant decrease in adenine nucleotide secretion (P < 0.01) and release of malonyldialdehyde (MDA), pro duced in equal amounts to TXA(2), in thrombin-stimulated platelets (P < 0.0 01). However, selenite did not change the level of MDA/TXA(2) in sodium ara chidonate-stimulated platelets. We conclude that the inhibitory effects of sodium selenite on platelet activation could be the result of decreased syn thesis and release of secondary agonists (TXA(2), ADP) in stimulated platel ets. It is also possible that sodium selenite blocks the release of arachid onic acid from platelet membranes via phospholipases.