Further Studies on the Renin and Angiotensinogen Reaction in Vitro

Abstract

Previously, the author and coworkers have reported that the angiotensin formation reaction was more rapid when renin was incubated with crude renin substrate than when incubated with plasma, and that Lineweaver-Burk type plots of the two incubation systems showed the existence of a competitive inhibitor to renin-angio tensinogen reaction in plasma. However, there were differences of constituents between plasma and crude renin substrate, i. e., electrolytes, proteins, and lipids. It was the aim of this study to determine what effects were exerted upon the reaction by such differring components. Porcine plasma, dialyzed porcine plasma, and crude renin substrate partially purified from porcine plasma were employed as the source of the angiotensinogen, and these were incubated with renin solution prepared from porcine kidney at pH 5.5 in the presence of EDTA and DFP. The angiotensin produced was measured by means of rat bioassay. The results were as following. 1) In order to observe the influence of sodium concentration on the reaction, plasma, dialyzed plasma and crude renin substrate were incubated respectively with renin solution under various concentrations of sodium chloride. The maximum rate of reaction was reached at about 150 mM of sodium chloride in every case ; however the reaction was the most rapid when crude renin substrate was employed. 2) In the presence of 146 mM of sodium chloride, no effect was shown upon the reaction by successive additions of posassium chloride, calcium chloride, and magnesium chloride within these physiological concentrations. 3) The rate of reaction decreased in proportion to the addition of porcine serum albumin or bovine γ-globulin. 4) The mode of influence of the bovine serum albumin for the reaction was examined by means of the Lineweaver-Burk type technique, and was shown to be competitive inhibition. 5) Crude lipid extracted from porcine plasma was added to renin-plasma or renin-crude renin substrate mixture, In neither incubation system did the lipid have any effect on the reaction. Furthermore, another crude lipid extracted from porcine kidney also had no effect on the reaction.