Activation of haemostasis by exercise, mental stress and adrenalin: effects on platelet sensitivity to thrombin and thrombin generation

Stress-induced activation of haemostasis may be involved in the triggering of acute coronary syndromes. We compared the effects of mental stress, dyna mic exercise and adrenaline infusion on platelet sensitivity to thrombin us ing flow-cytometric analysis of platelet fibrinogen binding in whole blood, and platelet aggregability using filtragometry ex vivo, in healthy volunte ers. Furthermore, we assessed thrombin generation [prothrombin fragment 1 2 (F1 + 2) and thrombin-antithrombin complexes in plasma] and thrombin act ivity (fibrinopeptide A in plasma). Exercise (bicycle ergometry) enhanced t hrombin-induced platelet fibrinogen binding (P < 0.05) and platelet aggrega bility (P < 0.01), and elevated F1 + 2, thrombin-antithrombin complexes and fibrinopeptide A (P < 0.05 for all three). Adrenaline infusion enhanced th rombin-induced platelet fibrinogen binding and platelet aggregability (P < 0.05), and elevated thrombin-antithrombin complexes (P < 0.05), whereas F1 + 2 and fibrinopeptide A levels were not significantly affected. Mental str ess increased platelet sensitivity to high concentrations of thrombin only, and produced small increases in levels of thrombin-antithrombin complexes. Time control experiments showed no important changes with repeated measure ments during rest. Platelet responses to exercise and adrenaline were rever sible, with recovery 60 min later. Thus, heavy exercise and high levels of adrenaline reversibly increased platelet aggregability and platelet sensiti vity to thrombin, and enhanced thrombin formation; the effects were most pr onounced during exercise. Mental stress only weakly affected these paramete rs.