Plasma concentration and the depressor response to bradykinin infusion

To determine the relationship between vascular response and plasma levels of kinins, 10 anesthetized mongrel dogs received an intravenous infusion of bradykinin in graded doses (0.3 to 10.0 μg/kg/mm). Arterial pressure was recorded and plasma kinins determined by radioimmunoassay. There was a significant (p < 0.001) correlation between the increment in plasma kinins and the decrement in blood pressure which stabilized within five minutes. At the highest dose, arterial blood pressure fell by 37 ± 5 mmHg, and plasma kinins had risen by 1.5 ± 0.4 ng/ml. The magnitude of the change in plasma kinin levels observed in this study is similar to that acutely reported with administration of converting enzyme inhibitors. Thus, kinins may contribute to the hypotensive effect of these agents.