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Simultaneous Measurement of PRA, PRC and PRR and the Relation of Renin Reaction Rate to Renin Substrate Concentration

1980; Informa; Volume: 2; Issue: 1 Linguagem: Inglês

10.3109/10641968009038552

0148-3927

David B. Gordon, I. N. Sachin,

Renin-Angiotensin System Studies

AbstractWe have altered the method for measuring plasma renin concentration (P.R.C.) originated by Haas, et al (7) by using radioimmunoassay of angiotensin I and avoiding the addition of extrinsic renin substrate. Thus modified, the method gives valuers for P.R.A. (plasma renin activity), P.R.C. (plasma renin concentration), and also P.R.R. (plasma renin reactivity), which is the rate of reaction of renin substrate in the plasma with added extrinsic renin. By applying this modified method to a wide variety of plasma samples and independently measuring plasma renin substrate samples and independently measuring plasma renin substrate concentration (P.R.S.) in the same samples, we found a good correlation between P.R.R. and P.R.S. Our results indicate that the rate of the renin - renin substrate reaction in human plasma is proportional to renin substrate concentration over a wide range of values up to 5000 ng angiotensin I/ml or higher. Thus, first order reaction kinetics with respect to substrate concentration is followed even at high substrate levels and the Km must be high. An additional finding was that pregnant women have elevated P.R.C. levels in contrast with women taking oral contraceptives who have P.R.C. levels lower than normal.