[Problems in measuring parameters of the fibrinolytic system: circadian rhythm of tissue-type plasminogen activator and plasminogen activator inhibitor].

Reference values of tissue-type plasminogen activator (t-PA) antigen, t-PA activity, and plasminogen activator inhibitor (PAI) were established in healthy blood donors using different assay systems. Significant differences between male and female donors were found, due to the intake of oral contraceptives. PAI-activity determinations, using the method described by Chmielewska et al. (1983) or the modification by KabiVitrum, were only poorly correlated (r = 0.53; N = 98; p greater than 0.0001). PAI-activity (Chmielewska et al. 1983) determinations and t-PA antigen measurements were also significantly correlated (r = 0.52; N = 96), which may be a consequence of a joint regulation. In a second series, the diurnal variations of t-PA and PAI were investigated in blood donors (N = 83). PAI-activity and t-PA antigen were about 30 to 40 percent decreased in the evening hours, when compared with the morning values. In two controlled studies, the acute effects of heparins and desmopressin (DDAVP) on the fibrinolytic system were investigated in healthy individuals (N = 10). Again, a pronounced diurnal variation of t-PA and PAI was found. PAI and t-PA were significantly higher in the morning when compared with the evening. However, t-PA activity (Verheijen et al. 1982) showed a reversed pattern, low levels were found in the morning and increased levels in the evening. Our studies clearly show that when determining parameters of the fibrinolytic system, the diurnal variations have to be taken into account.(ABSTRACT TRUNCATED AT 250 WORDS)