[Effect of prethrombin I and prostaglandin E2 on thrombin-stimulated aggregation of rat platelets]

Effect of inactive precursor of alpha-thrombin--prethrombin (Pre-I) and prostaglandin (PGE2) on aggregation of washed rat platelets induced by alpha-thrombin was studied. Pre-I inhibited dose-dependently the alpha-thrombin-induced platelet aggregation. K1 values for Pre-I of high and low affinity binding sites were equal to 0.9.10(-8) M and 0.56.10(-6) M, respectively. PGE2 inhibited the alpha-thrombin-induced aggregation after simultaneous addition and within 5 and 15 min of incubation with PGE2. Preincubation of platelets with alpha-thrombin within 15 min prevented the PGE2-induced aggregation but preincubation of platelets with Pre-I within 15 min did not influence the platelet aggregation, induced by PGE2.