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The effect of aspirin or endotoxin or aspirin plus endotoxin on the circadian variations of plasminogen activator activity (PAA), tissue-type plasminogen activator (t-PA) antigen level, plasminogen activator inhibition (PAI) and plasmin inhibition (PI) in aorta, heart and brain of the rat was studied. In aorta the circadian variations of PAA, t-PA antigen and tissue-type PAI (t-PAI) were blunted by endotoxin, while the circadian variation of PI was reversed; t-PAI variation was blunted by aspirin plus endotoxin, while PI variation was reversed. Various disturbances of the circadian variations of PAA, t-PA antigen, PAI or PI in heart and brain were also observed. In conclusion, the circadian variations of fibrinolytic parameters in key organs are influenced by aspirin or endotoxin or aspirin plus endotoxin in a varying way or degree depending on the treatment, the parameter studied or the organ.

Plasminogen activator activity (PAA), plasminogen activator inhibition (PAI) and plasmin inhibition (PI) have been studied with spectrophotometric methods in extracts of human, bovine, ovine and rat kidneys of both sexes. In all species studied, renal PAA (cortex or medulla) was higher in females than in males. The PAA was also higher in the medulla than in the cortex in all species and both sexes. The PAA was due to both types of plasminogen activator; tissue-type plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA). In the human kidney (cortex or medulla) the measurement of t-PA antigen showed that t-PA is higher in females than in males; t-PA is also higher in the medulla than in the cortex in both sexes. The PAI showed the opposite pattern in all species studied; it was lower in females than in males. It was also lower in the medulla than in the cortex. PAI-1 was identified in the human kidney. Sex-related differences in renal PAA or PAI almost disappeared after bilateral orchidectomy in rats. PI showed no sex or regional differences in the species studied. Sex-related differences in renal PAA and PAI in man and various animal species might be of physiological or pathophysiological importance.

Marked changes of the plasminogen activator activity, plasmin inhibition, and plasminogen activator inhibition were found in fatty streaks and fibrous plaques compared to the normal intima of the human aorta. Plasminogen activator activity and plasmin inhibition showed the following pattern: fibrous plaques greater than fatty streaks greater than normal intima. Plasminogen activator inhibition showed the opposite pattern: normal intima greater than fatty streaks greater than fibrous plaques. The tissue-type, but not the urokinase-type, plasminogen activator was detected immunologically.