A Method of Radioimmunoassay of Plasma Angiotensin II Using Florisil

Abstract

Several methods for determination of angiotensin II (AII) in human plasma had been reported. Most popularized method was extraction method using Dowex (H+) resin. Direct method and extraction method using acetone-petroleum ether were also used. However these methods have several defects, such as intricate procedure, low sensitivity or low rate of extraction. Therefore we developed a new method for AII in human plasma which was used florisil adsorption and elution with acetone-hydrochrolic acid solution.In our method compared with the method using acetone-petroleum ether or the direct method, the extraction rate was 84% and minimum detectable value was 0.75pg/tube (B/Bo 95% intercept value).Reproducibility of intra-assay and inter-assay were 11.7% and 12.9%, respectively. This our method was more sensitive, specific and simple, and was useful for routin clinical investigation.We studied the untreated 21 patients with essential hypertension (containing 11 males and 10 females, their averaged age was 41.5 years old, and blood pressure on admission was 175.8/112.5mmHg).We measured plasma renin activity (PRA) and AII (florisil-method) in venous blood before and after intravenous injection of 20mg furosemide and oral administration of 25mg captopril. After the furosemide administration, All in venous blood significantly increased to 35.0 8.0pg/ml (Mean±SE) from 14.6±2.6pg/ml (p<0.001), and PRA also increased to 2.40 0.89ng/ml/hr from 0.92±0.21ng/ml/hr. Although after captopril administration PRA significantly increased to 2.56±1.02ng/ml/hr from 1.05±0.32ng/ml/hr (p<0.01), All decreased to 8.2±2.2pg/ml from 15.2±3.1pg/ml (p<0.001). Moreover, All levels in arterial and venous blood were 27.8±7.8pg/ml and 28.8±6.7pg/ml, respectively.