In vitro Degradation of I131 Labeled Angiotensin II by Normotensive and Hypertensive Human Serum.

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Abstract
Mixtures of sera from either normotensive subjects or from patients with untreated primary benign hypertension and varying quantities of angiotensin II-I131 were incubated in vitro. After the proteins were stained with brom phenol blue the solutions were analyzed by radiochromato-electrophoresis. An automatic strip scanner using a thin window gas flow counter was employed to assay the radioactivity of the substances on the strips and the mobilities of these substances were compared with that of unaltered angiotensin II-I131. Two separate peaks of radioactivity were present in the mixtures and by measurement of the areas beneath these peaks, the amounts of unaltered angiotensin II-I131 (with the slower mobility) and iodine-131 which is the end-product of angiotensin II-I131 degradation (with the faster mobility) were determined and the per cent angiotensin II-Il31 degraded was calculated. Greater quantities of angio-tension II-I131 were degraded by the untreated primary benign hypertensive patients than by the normotensive subjects. Two patients with secondary renal hypertension had percentages of angiotensin II-I131 degradation within the normotensive range. The greater in vitro degradation of angiotensin II-I131 by the untreated primary benign hypertensive patients than by normotensive subjects contrasts with the in vivo turnover rates. This in vitro technique may provide a simple rapid radiochemical distinction between normotensive, primary benign hypertensive, and secondary renal hypertensive subjects.