Fluctuation of TPA and PAI-1 antigen levels in plasma: difference of their fluctuation patterns between male and female.

The daytime fluctuation of the fibrinolytic activity and the antigen levels of tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1 (PAI-1) in plasma were analyzed in normal male and female volunteers. Samples were obtained at 8:30, 10:30, 12:30, 14:30 and 16:30 h. Euglobulin clot lysis time (ECLT) showed the longest time at 8:30 to 10:30 h and the shortest time at 16:30 h. The highest level of tPA was obtained at 8:30 h and the lowest at 14:30 h in men, whereas the highest value was at 8:30 h and the lowest was at 16:30 h in females. Active free PAI-1 showed highest value at 10:30 h in men and at 8:30 h in women. The lowest values obtained at 16:30 h in both men and women and were about one third of the highest values. ECLT was always shorter in females than in males and parameter such as tPA and PAI-1 were also lower in females than in males. The phase of the circadian rhythm of the fibrinolytic parameters may be advanced in females than in males.