Metabolism and distribution of I-131-labeled angiotensin II.

Abstract

Abstract Angiotensin II-I 131 has been employed to study the metabolism of this polypeptide quantitatively. Labeled angiotensin II has been administered intravenously to 11 subjects with normal blood pressure, 7 patients with untreated primary benign hypertension, and to one patient with each of the following: treated primary benign hypertension, primary accelerated hypertension, pheochromocytoma before and after surgical resection, secondary renal hypertension, and one who previously had hypertension associated with acute glomerulonephritis. The normotensive subjects had a mean value for the final space of distribution of angiotensin II of 23 L., a mean half-time of the rate of disappearance of the major component of angiotensin II of 10.3 hours, and a mean total exchangeable angiotensin II pool of 0.41 μg. Comparable results in the primary untreated hypertensive subjects were 26 L., 15.8 hours, and 0.99 μg. The degradation of angiotensin II-I 131 in these experiments followed first order kinetics. The slow angiotensin degradation rate in patients with primary untreated hypertension may be responsible for the increased concentration and quantity of this peptide in their body fluids.