A Sensitive Method for Assay of Plasma Renin Activity

Renin activity is separated from rabbit plasma by globulin precipitation, dialysis, and DEAE cellulose column chromatography with a Tris chloride buffer system and acid elution, followed by ultrafiltration. The plasma renin extract contains no renin substrate and no angiotensinase activity can be detected after incubation with angiotensin for 200 hr. Incubation with a known concentration of rabbit renin substrate, similarly free of renin activity and angiotensinase, at pH 6.0 in 0.1 M phosphate buffer forms angiotensin-like activity at a constant rate for up to 200 hr. Recovery and reproducibility are satisfactory. Evidence is presented that the material in the plasma extract behaves similarly to renin and that the incubation product is indistinguishable from angiotensin.