A Vasodepressor Peptide in Cohn Fraction III-0 of Human Plasma Proteins

Abstract

Previous reports (1,2) have described the ability of human plasma to cause constriction in an isolated perfused vein from the rabbit ear. The activity emerges as a single peak from a Sephadex G200 column when high molality buffer is used, in a fraction suggesting a molecular weight of approximately 100,000. The original plasma and the eluate containing venoconstrictor activity are also vasodilator in the intact vascular beds of the guinea pig heart and the dog hind limb and on several other preparations behave very like bradykinin. Similar activity is also found in several Cohn fractions of human plasma proteins, the richest source being fraction III-0 the major components of which are partly denatured β-lipoproteins. The activity from this source is however readily dialysable and this paper describes the partial isolation of an active peptide from it.