EPINEPHRINE AUGMENTS PLATELET RECRUITMENT TO IMMOBILIZED COLLAGEN IN FLOWING BLOOD - EVIDENCE FOR A VAN WILLEBRAND FACTOR-MEDIATED MECHANISM

Although elevated plasma epinephrine (epi) levels are associated with clinical atherothrombosis, the role of epi in platelet-vessel wall int eraction has not been established. Our aim was to study the effect of high physiological epi (10 nM) in an experimental model which tests th e interaction between platelets and immobiIized collagen in whole bloo d. Shear forces and anticoagulation were modulated. Epi significantly enhanced platelet deposition, but only at high shear rate (1.600 s(-1) ). In PPACK- or LMWH-anticoagulated blood, the increase in platelet de position was 32 to 85 % (p <0.02-0.05). Furthermore, platelet aggregat ion was cotriggered with subthreshold concentrations of epi and ristoc etin, and monoclonal antibodies against glycoprotein (GP) Ib (AN 51 an d SZ 2) attenuated epi-induced aggregation. We conclude that epi is ca pable of augmenting platelet functions, which are dependent on the int eraction of vWF with GP Ib and GP IIb/lIIa. Via this mechanism epi may promote arterial thrombosis in vivo.