Abstract
Summary
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 two renin substrates: a major one with a molecular weight of 65,000, and a minor one, amounting to 3-5% of the quantity of the major peak, with a molecular weight of 450,000 to 500,000. In women taking oral contraceptives, the same two peaks of renin substrate are seen, but the quantity of each is increased significantly. In pregnant women at term, in addition to the other two renin substrates a third 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 poly-acrylamide gel electrophoresis which, as previously reported (1), shows the presence of five renin substrates. However, both techniques confirm the presence of multiple renin substrates in human plasma.
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