title: Diurnal variation of the fibrinolytic system.
abstract: To elucidate which component(s) of the fibrinolytic system is (are) responsible for the diurnal variation of fibrinolytic activity we have studied several parameters of this system in 8 healthy male volunteers during a period of 24 h. Blood was collected at 8 a.m., 10 a.m., 12 a.m., 4 p.m., 8 p.m. and 8 a.m. next morning. The following tests were performed: euglobulin clot lysis time (ECLT), fibrinolytic activity of euglobulins on fibrin plates in the presence and absence of blocking antibodies to tissue-type plasminogen activator (t-PA) and/or urokinase (u-PA), overall plasminogen activator inhibitor (PAI) activity, antigen levels of t-PA, u-PA and PAI-1 and zymography of the euglobulin fraction after SDS-PAGE. From 8-10 a.m. to 4-8 p.m., total fibrinolytic activity increased by 113% (p less than 0.01) or 71% (p less than 0.01) when measured by ECLT or by fibrin plate assay, respectively. The immunoquenching experiments showed that this increase was entirely due to t-PA related activity whereas u-PA activity and t-PA/u-PA independent activity remained constant during the day. Average antigen levels of u-PA and t-PA in the afternoon were 6% and 25% lower than those measured in the morning. During this period, overall PAI activity and PAI-1 antigen decreased by 31% (p less than 0.01) and 52% (p less than 0.01) respectively. Electrophoretic-zymographic analysis of the euglobulins revealed that throughout the day the majority of t-PA was present in the form of the 110 kDa t-PA/PAI-1 complex. The intensity of this complex was lowest in the afternoon.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000293:Adolescent; D000328:Adult; D000941:Antigens / Q000032:analysis; D002940:Circadian Rhythm; D004591:Electrophoresis, Polyacrylamide Gel; D005342:Fibrinolysis; D006023:Glycoproteins / Q000097:blood / Q000276:immunology; D006801:Humans; D008297:Male; D010960:Plasminogen Activators / Q000037:antagonists & inhibitors / Q000097:blood / Q000276:immunology; D015849:Plasminogen Inactivators; D012712:Serum Globulins / Q000032:analysis; D010959:Tissue Plasminogen Activator / Q000097:blood / Q000276:immunology
chemical_list: D000941:Antigens; D006023:Glycoproteins; D015849:Plasminogen Inactivators; D012712:Serum Globulins; D010960:Plasminogen Activators; D010959:Tissue Plasminogen Activator