Characterization of a radioimmunoassay to determine plasma total renin.

The determination of plasma total renin is useful not only as a tool to investigate the physiology of hypertension but also as a marker for Wilms' tumor. A radioimmunoassay (RIA) system to determine plasma total renin was newly developed using monoclonal antibodies specific for both inactive and active renin (inactive + active = total); in this study, an effort was made to confirm that this RIA system truly determines plasma total renin concentrations. First, it was found that this monoclonal antibody stains only the juxtaglomerular apparatus of the kidney. Second, the data determined by the RIA were compared with those obtained by the conventional enzymatic method: samples were activated, and renin activity was assayed by measuring angiotensin I. The coefficient of the data obtained by this RIA system and by the conventional method was 0.921 (p less than 0.01) based on all 89 samples, and 0.809 (p less than 0.01) based on 86 of the 89 samples whose values were less than 600 pg/ml by RIA. As a result of these studies, it was concluded that the newly developed RIA system does determine total renin levels in patients' plasma.