Estimation of Angiotensin II Concentration in Human Plasma by Radioimmunoassay. Some Applications to Physiological and Clinical States

A radioimmunoassay method for the measurement of angiotensin II in human plasma is described. The hormone is extracted quickly by Dowex (H + ) particles. Angiotensinase and converting enzyme are inhibited by a mixture of EDTA and o‐phenanthroline. Blood samples can be processed at room temperature. Recoveries from blood were 83%± 11 (SD), n =44. Replicates within one assay varied about their mean with a standard deviation of ± 10%, n=16. The smallest concentration detectable, using 10 ml plasma samples, was 2 pg/ml plasma. Peripheral venous plasma concentrations in 33 normal adults ranged from 5 to 35 pg/ml. Plasma angiotensin II concentrations in some physiological and clinical conditions are reported.