[Effect of SIN 1 on the interactions of endothelial cells and thrombocytes]

A new method has been developed to investigate the direct effect of endothelial cells on platelet aggregation in the presence of cultured confluent human EC monolayers. The inside of the disk shaped cuvettes are covered by human umbilical vein ECs. The cuvettes rotate in the light beam of a photometer. In these cuvettes the effect of different aggregation inducers was inhibited in a concentration-dependent manner, e. g. for collagen at 0.5 microgram/ml, ADP at 5 x 10(-7) M, epinephrine at 5 x 10(-7) M and thrombin at 0.05 U/ml final concentration. (Platelet count 5 x 10(5)/microliters). Higher concentrations of the inducers led to irreversible platelet aggregation and were used for testing of antiplatelet drugs. In this system we detected a synergism between the antiaggregatory effect of the EC monolayer and that of SIN 1 (Cassella, Frankfurt/Main) the main metabolite of Molsidomine. 10 micrograms/ml PRP of SIN 1 alone partially inhibited platelet aggregation induced by 1 microgram/ml collagen and 10(-6) M ADP respectively in uncovered aggregation cuvettes. In the presence of an EC monolayer complete inhibition of platelet aggregation was obtained at a 5-fold final concentration of both inducers. After pretreatment of ECs with 1 mmol ASA over 30 min. the antiaggregatory effect of SIN 1 decreased, but was more pronounced (50%) than in uncovered cuvettes (25%).