Synergistic effect of endothelin-1 and serotonin in rabbit platelets:: Effect on tyrosine phosphorylation

The effect of endothelin-1 on protein tyrosine phosphorylation was partially inhibited in rabbit platelets, in the presence of ET(A) receptor antagonists. After a sarafotoxin S6c treatment (an ET(B) receptor agonist), a minor effect, compared with the endothelin-1 effect, was found. On the other hand, pre-treatment of platelets with endothelin-1 resulted in an enhancementin serotonin-promoted protein tyrosine phosphorylation. Moreover, in rabbit platelet membrane, endothelin-1 induces a concentration-dependent serotonin binding enhancement and inhibition of its internalization. Thus, endothelin-1 may act as a partial agonist with serotonin through A and B components for a putative endothelin-1 receptor in rabbit platelets.