Mechanisms underlying the exercise-induced increase in tissue plasminogen activator (t-PA) levels are still controversial and the role played by adrenergic activation and metabolic acidosis in endothelial t-PA secretion is under discussion. Fibrinolytic parameters and catecholamines were investigated in 20 untrained healthy males who performed a well-standardised treadmill stress test with the continuous measurement of cardiorespiratory and metabolic parameters for the exact determination of anaerobic threshold (AT). Components of the fibrinolytic system showed only slight modifications during the aerobic phase of the exercise in spite of a marked increase in adrenaline levels (+127%). Only after the reaching AT euglobulin lysis time, did t-PA (activity and antigen) and plasminogen activator inhibitor (PAI-1) (activity and antigen) become clearly different from baseline and t-PA increase was more marked than adrenaline rise. Thirty minutes after the end of exercise t-PA levels were still higher than baseline, whereas adrenaline levels quickly normalised. Thus, the exercise-induced secretion of t-PA seems to be related not only to adrenergic activation per se but also to metabolic acidosis, which is at least in part adrenaline-induced.
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