THE ISOLATION FROM HUMAN BLOOD PLASMA OF A SUBSTANCE HAVING POSITIVE INOTROPIC ACTION ON THE ISOLATED TOAD HEART

Abstract

The substances responsible for the positive inotropic activity of normal human blood plasma on the isolated toad heart were separated into a high-molecular-weight (greater than 60,000) and low-molecular-weight (4,000-10,000) fractions by gel-filtration on Sephadex or 5% cross-linked poly-acrylamide gel. A highly active substance was isolated by ion-exchange chromatography on a 5% cross-linked polymer of acrylamide, NN-methylenebisacrylamide and diethylaminoethyl methacrylate. The initial gel-filtration experiments were carried out under a wide variety of conditions and resulted in the same yield of high-molecular-weight and low-molecular-weight fractions with inotropic activity. It was concluded that it was unlikely that the low-molecular-weight fraction with inotropic activity was an artifact produced from the plasma proteins by the method of isolation. The inotropic activity of the isolated substance was destroyed by incubation with protease.