Platelet activation and secretion with emotional stress
Platelets are believed to play a role in the pathogenesis of atherosclerosis and of the vascular obstruction that causes the acute complications of coronary artery disease. Since specific behavioral patterns appear to be related to the development of coronary artery disease and since emotional stress may predispose an individual to acute cardiovascular ischemia, it was hypothesized that platelet activation by catecholamines might be involved in these events. To study emotional stress, plasma samples were obtained from 61 senior medical residents immediately before they were to speak in public. There were significant increases in the plasma concentrations of the platelet-secreted proteins platelet factor 4 and beta-thromboglobulin and epinephrine and norepinephrine immediately before speaking, which demonstrates that platelet activation and secretion occur in association with this type of emotional stress. Four trials were carried out to study the mechanism for this observed platelet secretion: (1) phenoxybenzamine, (2) propranolol, (3) 650 mg aspirin, and (4) 80 mg aspirin were given several hours before the public speaking engagement. Neither phenoxybenzamine nor propranolol in doses that blocked the hemodynamic effects of alpha 1- and beta 1-adrenergic stimulation modified platelet secretion. Aspirin also did not block platelet secretion, which suggests that platelets were not being stimulated through a cyclooxygenase-dependent pathway. This study provides direct evidence of platelet secretion in vivo in association with emotional stress, and underscores the potential importance of platelet activation and secretion in the acute events that occur in patients with vascular disease.