Chromatographic Separation of Multiple Renin Substrates in Women: Effect of Pregnancy and Oral Contraceptives

Abstract

Proteins in blood plasma of women were separated by chromatography on a column of Sephadex G-200, and the amount of renin substrate in each fraction was determined. The molecular weight of the peaks of renin substrate found was estimated by comparison with the elution position of proteins of known molecular weight. Plasma of normal nonpregnant women shows the presence of 2 renin substrates: a major one with a MW of 65,000, and a minor one, amounting to 3-5% of the quantity of the major peak, with a MW of 450,000 to 500,000. In women taking oral contraceptives the same 2 peaks of renin substrate are seen, but the quantity of each is increased significantly. In pregnant women at term, in addition to the other 2 renin substrates a 3rd renin substrate of intermediate size is present. Its molecular weight is approximately 350,000 daltons. It sometimes overlaps and obscures the peak of high molecular weight renin substrate. The quantities of the intermediate and low molecular weight renin substrates are greatly increased in pregnancy. The resolution of renin substrates in plasma by gel chromatography is somewhat less than that achieved by polyacrylamide gel electrophoresis which, as previously reported, shows the presence of 5 renin substrates. However, both techniques confirm the presence of multiple renin substrates in human plasma.