1. Intravascular coagulation in the kidneys of rats was induced by intravenous infusion of thrombin and by inhibition of fibrinolysis with tranexamic acid under α-chloralose anaesthesia. The amount of fibrin in the kidneys was measured with radioactively labelled fibrinogen. Chronic saline loading and inhibition of angiotensin II (ANG II) with saralasin reduced the fibrin deposition in the kidneys. Infusion of ANG II had the opposite effect.
2. Renal and aortic blood flows were measured by injection of radioactively labelled microspheres. After thrombin infusion the renal and aortic blood flows were reduced to about one-third of the pre-infusion values. Chronic saline loading diminished these changes, but saralasin had no effect.
3. Plasma renin activity (PRA), measured by radioimmunoassay, decreased by about 50% after thrombin infusion.
4. The reduction in PRA and the lack of effect of saralasin indicate that the renin—angiotensin system is not the mediator of the observed decrease in the renal blood flow. As saralasin reduced the amount of fibrin the mechanism regulating fibrin deposition appears to be independent of the mechanism that reduces the renal blood flow.
