ABSTRACT
BACKGROUND AND PURPOSE: Among the many factors having influence on seasonal incidence of thrombotic disease, we studied the seasonal variation of fibrinolytic activity, which might be thought to have influence on seasonal incidence of thrombotic disease. SUBJECT AND METHOD: Seasonal plasma tissue type plasminogen activator (t-PA) and euglobulin fibrinolytic activity (EFA) were measured in 18 male and 22 female normal volunteers during a year. RESULT: The level of t-PA was higher in winter than in spring (p<0.05), but was not significantly different in the other couples of four seasons. The level of EFA was higher in winter than in summer and in autumn (p<0.01), and was slightly higher in winter than in spring without significance. The level of EFA was higher in spring than in summer (p<0.05). There was no correlation between the level of t-PA and that of EFA in any of the seasons. CONCLUSION: The fibrinolytic activity is higher at lower temperature than at higher temperature. Thus, it seems that a rise in fibrinolytic activity in cold weather counters certain changes which make a thrombotic event.