Comparison of angiotensin I and angiotensin II antibody trapping methods for determination of plasma renin concentration and activity.

Comparative determinations were made of the renin activity of human blood plasma by applying a radioimmunoassay of angiotensin I and angiotensin II, and also by parallel determinations of PRA I and PRA II. To protect the angiotensin generated in plasma, the antibody trapping method was used. The concentration of renin was also determined. It was found that, under the experimental conditions applied, when determining PRA II the renin was gradually inactivated in plasma; when determining PRA I it was protected by EDTA added to plasma. Thus PRA II is present to a lesser degree than PRA I. The experiemnts performed have confirmed the advantages of determining PRA I by the antibody trapping method.