Effects of hyperthermal stress on the fibrinolytic system

The effects of hyperthermal stress on the coagulation and fibrinolytic systems were examined in five healthy subjects who took a 3-min 47 degrees C hot-spring bath. After a 3-min 47 degrees C bath, the sublingual temperature was transiently increased about 1.8 degrees C, returning to the baseline level within 60 min. The plasma level of plasminogen activator inhibitor-1 antigen (PAI-1) was transiently increased 15 min after the start of bathing and returned to the pre-bathing level 360 min later. The plasma levels of tissue plasminogen activator antigen, alpha 2 plasmin inhibitor activity, plasmin-antiplasmin complex, thrombin-antithrombin III complex, and thrombomodulin antigen were not influenced by the bath. The in vivo result correlated well with the in vitro result that PAI-1 was released from cultured endothelial cells by heating. These findings suggest that the increase in plasma PAI-1 level may be due to the direct hyperthermal action of the very hot hot-spring bath on the endothelial cells and that acute hyperthermal stress may decrease the fibrinolytic capacity, leading to the occurrence of thrombotic events.