SELECTIVE RENAL VASCULAR EFFECTS OF ETHACRYNIC ACID

¹ Departments of Medicine (Clinical Pharmacology) and Pharmacology, Emory University School of Medicine, Atlanta, Georgia

The effects of ethacrynic acid on canine renal and femoral blood flows and on blood flow responses to i.a. injections of acetylcholine and norepinephrine were studied. Kidneys and limbs were denervated; flow was measured with an electromagnetic flow meter; and pressure was varied by aortic constriction. Ethacrynic acid completely abolished renal autoregulation. However, unlike vasodilators in general, it neither increased renal blood flow at reduced perfusion pressure (less than 80 mm Hg) nor dilated the limb vessels. We suggest that ethacrynic acid may act indirectly by interfering with normal intrarenal circulatory control mechanisms. The vascular reactivity of the kidney was found to be selectively reduced by ethacrynic acid. Local arterial angiotensin infusion during ethacrynic acid diuresis significantly enhanced renal reactivity to norepinephrine, whereas hind limb responses were not affected in a similar manner. These observations suggest that resistance is a determinant of vascular responsiveness in the kidney but not in the limb. The renal vascular effects of ethacrynic acid may be significant in the therapy of heart failure and shock.