[Inhibition of thrombocyte spreading and the formation of thrombus-like aggregates bound with substrate by the anti-anginal agent trapidil]

Abstract

Effects of trapidil (rocornal) on interaction of human thrombocytes, purified by gel filtration, and the surface covered with fibrillar collagen from calf skin (CCS) were studied using scanning electron microscopy. When the soluble inductors were absent, trapidil did not affect the thrombocyte adhesion. At the same time, trapidil inhibited the shape alterations of laminated thrombocytes, induced by CCS-substrate with simultaneous increase in the ratio of disc-shaped cells and a decrease in laminated thrombocytes. Soluble inductors of the thrombocyte activity (arachidonic acid, stable derivative of prostaglandin endoperoxides U46619 and thrombin) stimulated the cells mass-scale lamination as well as formation of thrombus-like aggregates bound with CCS-substrate. Trapidil prevented completely the effects of exogenous arachidonic acid and of U46619 on interaction of thrombocytes and the substrate but inhibited only by 40-50% the synthesis of thromboxane A2 in the cells induced by arachidonic acid. The drug blocked also an aggregation of thrombocytes in suspension, lamination and formation of aggregates bound with the surface, induced by low but not by high concentrations of thrombin. Possible use of trapidil is discussed.