Coordinate Activation of Human Platelet Protease-activated Receptor-1 and -4 in Response to Subnanomolar α-Thrombin*

We previously demonstrated that human platelets activated with SFLLRN release PAR-1 activation peptide, PAR-1-(1-41), even in the presence of hirudin. This observation suggests that during their activation, platelets generate a protease that activates PAR-1. In this study, PAR-1 and -4 activation peptides were detected 10 s after