Extraction, purification, and assay of human renin free of angiotensinase.

Three procedures are described for the extraction and purification of renin from 0.05 to 500 g of human kidneys. A uniform yield of renin, free of angiotensinase, resulted from all three procedures. All tests for renin were carried out in dogs. When more than 10 g of renal tissue was used, renin was determined by the direct method; with smaller amounts, the indirect method, involving the production and the assay of angiotensin, was employed. Renin substrate free of angiotensinase, suitable for the indirect assay of human renin, was prepared from pooled human serum by a simple procedure. The angiotensinase-free renin and substrate permitted prolonged incubation for the production of the angiotensin required for the indirect assay. The mean ratio of angiotensin produced (unit per milliter of serum) to the amount of renin added (unit per milliliter of serum) was 1,482 for an 18-hour period of incubation. The large amount of angiotensin produced permitted the indirect assay of minute amounts of human renin (as little as 0.0005 unit, from 5 mg of renal tissue) in the dog. Unless the angiotensinase present in extracts of renal tissue or serum is first removed, the accurate, indirect assay of the renin is not possible. ADDITIONAL