Kinetic studies on renin-angiotensinogen reaction after nephrectomy

Abstract

The injection of renin into a rat nephrectomized 24 hr previously potentiates the pressor response of this enzyme due to an increased production of angiotensin. In vitro renin produces a greater amount of angiotensin from plasma of nephrectomized than from that of normal rats. To evaluate the basis for this difference, kinetic studies on the renin-angio-tensinogen reaction were made which included measurements of the Michaelis constant. The difference in rate of angiotensin formation was found to be due to a 15-fold difference between the substrate concentration in the plasma of normal and nephrectomized animals. No difference was detected between the "turnover numbers" or the K_m's for the action of hog renin on angiotensinogen from these two sources. The turnover number for hog renin in the presence of hog or rat plasma is similar even though the K_m of the enzyme is significantly different for the two substrates.