Acute effects of angiotensin II on fibrinolysis in healthy volunteers.

Recent studies have suggested that angiotensin II may inhibit fibrinolysis. In order to further test this hypothesis, we investigated the acute effects of angiotensin II (intravenous infusion of 10 ng/kg per min over 15-20 min) on fibrinolytic function in 18 healthy men. Time-controls (n=11) and control experiments with a placebo infusion (n = 13) were also performed. The activities of plasmin activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA), as well as t-PA antigen levels, were determined in plasma before, during and 60 min after the infusion of angiotensin II. Angiotensin II caused a clear-cut elevation in blood pressure; heart rate and plasma noradrenaline levels tended to decrease during the infusion but increased afterwards, indicating reflexogenic adjustments. Plasma t-PA activity and antigen levels increased by 81+/-11 and 14+/-3%, respectively, during angiotensin II infusion (both P < 0.001), whereas t-PA activity was unchanged and t-PA antigen decreased (P < 0.05) in placebo experiments. PAI-1 activity decreased similarly in time-controls and during angiotensin infusion (P < 0.001). Thus, short-term infusion of angiotensin II enhances fibrinolysis by elevating plasma t-PA. It is not clear whether this is a direct angiotensin-receptor-mediated effect or if it is related to the hemodynamic effects of the infusion.