PREPARATION AND BIOASSAY OF RENIN

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Abstract
A fractional precipitation method, employing NaCl and ammonium sulfate, for the extraction and purification of renin, was described. Organic solvents were not employed in this procedure. The final product obtained was a non-toxic pressor protein apparently belonging to the globulin group. The protein retained its pressor properties unimpaired for long periods if kept solidly frozen, or if lyophiled and kept in the dry state as a powder under vacuum. The frozen or dried material contained 4 to 6 mg. of solids per ccm. The total N content was 15.4 to 15.7% of the total solids. The pressor principle was non-dialyzable and was positive for all of the standard protein tests. A relatively pure and stable prep. of renin was assayed at various dosage levels (0.1, 0.2, 0.3, and 0.4 mg. solids per kg. body wt.) on dogs, and a unit established. A renin unit was defined as the minimum amt. necessary, when given intraven. over a period of 2 to 5 sees., to raise the mean arterial pressure of anesthetized dogs an avg. of 40 mm. Hg above the starting pressure level. This unit, in terms of the prep. used, was equivalent to 0.1 mg. solid material per kg. body wt. and contained 0.016 mg. N. The blood pressure response to renin injs. was directly proportional to dosage for all levels tested, up to and including the 0.3 mg. level. Higher doses did not give proportional pressor responses. Various factors which modify the pressor response, such as starting level of pressure, rate of inj., etc., were discussed. The renin prep. employed was non-toxic even when intraven. inj. in large (35 mg.) amts.