On the relationship between aggregation and cyclic nucleotides in platelets treated with betaadrenoceptor blocking drugs.

The inhibition of aggregation of rat platelets treated with betaadrenoceptor blocking drugs alprenolol, exaprolol, metipranolol, practolol and propranolol, and stimulated with adenosinediphosphate was shown to be dose-dependent. Atenolol in all concentrations potentiated the aggregation. The stimulated aggregation was potentiated by low and decreased by high concentrations of doberol. Cyclic adenosinemonophosphate was decreased in platelets treated with all the betaadrenoceptor blocking drugs used. On the other hand, a dose-dependent increase in the cyclic guanosinemonophosphate content was evident in betaadrenoceptor blocker-treated platelets. The interaction of betaadrenoceptor blocking drugs with the aggregation of blood platelets seems not to be mediated through cyclic nucleotides.