Physiological Properties of Renin and Hypertensin

Abstract

The physiological response of the normal, unanesthetized or anesthetized dog to the intraven. injn. and infusion of highly purified renin was investigated. This constitutes the basis for a direct, rapid, accurate and specific bioassay for renin at a level of 1 unit. It also includes a study of the effect of hypertensin under similar conditions and detns. of the hypertensinogen content of the blood before and after the intraven. injn. of renin. Exptll. conditions also were outlined for an indirect assay of renin at a level of 0.01 units. The sensitivity of the dog to renin and hypertensin is greatly reduced by anesthesia. Tachyphylaxis develops after repeated injn. of large doses of renin at short intervals, a condition characterized by progressively diminished pressor response to renin. There was no sign of tachyphylaxis when injns. of renin were spaced at intervals long enough to permit the blood pressure to return every time to the original base line. A sustained hypertension was elicited during the period of injn. by the constant infusion of renin at a rate of 0.5 units/min., an exptl. arrangement suitable for the investigation of acute hypotensive drug action. No change in the hypertensinogen concn. of the blood takes place under these conditions. In contrast, the continuous infusion of larger amts. of renin produces a rapid but temporary rise in blood pressure, accompanied by a depletion of serum hypertensinogen. Rapid disappearance of renin from the circulation was observed after the continuous intraven. injn. of large amts. of renin.