Measurement of plasma active renin by solid phase radioimmunoassay using monoclonal antibodies

A direct radioimmunoassay (RIA) for plasma active renin concentration (ARC) was evaluated by using plasma samples obtained from hospitalized normal volunteers and hypertensive patients. The direct renin RIA was performed by using a pair of anti-renin monoclonal antibodies and a sandwich method. It is suggested that an agitator should be used during the incubation, because the magnetic solid phase was precipitated and could not be suspended well in plasmas. Further, the thawed reagents should not be used for the assay. A highly significant correlation (r = 0.96, p less than 0.01) was found between ARC and enzymatic activity of renin (PRA) in plasma samples obtained from hypertensive patients. The mean values of ARC were 22.8 +/- 3.6 pg/ml in normal subjects, 22.5 +/- 5.3 in patients with EH having medium levels of PRA, 113.7 +/- 11.7 in patients with renovascular hypertension, and undetectable in patients with primary aldosteronism. The results indicated good and reliable performance of the direct renin RIA, which is clinically useful to investigate the renin-angiotensin system.