Circadian fluctuation of plasmatic plasminogen activator and its inhibitor PAI-1 of Japanese adults.

Circadian fluctuation of plasmatic tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI-1) in healthy 15 adults was examined for 24 hours. In comparison to t-PA level at 16:00, the level significantly increased at 8:00 and 9:00 (p<0.01), then gradually reduced to 1/2 by the late afternoon. PAI-1 level also markedly increased at 8:00 and 9:00 (p<0.01), then rapidly reduced to less than 1/3 of that level by 12:00 and the low level was maintained through afternoon to late at night. There were individuals showing steep drop of PAI-1 level from 8:00 to 12:00. It was concluded that plasma fibrinolysis was regulated by PAI-1 rather than t-PA in physiological fibrinolysis and that interpretation should be careful of the analysis of fibrinolysis particularly of PAI-1 because of its marked circadian fluctuation.