Relationship of Plasma Peptides to the Myocardial Depressant Factor in Hemorrhagic Shock in Cats

Abstract

The pathophysiological relationships of a myocardial depressant factor (MDF) present in the plasma of cats in hemorrhagic shock were studied. Aprotinin (Trasylol), an inhibitor of a variety of proteases including kallikrein and trypsin, prolonged survival of cats in postoligemic shock as well as prevented the appearance of MDF in the plasma. Trasylol did not alter the arterial blood pressure, venous pressure, or heart rate of these cats in shock, nor did it protect by exerting a positive inotropic effect. Trasylol was ineffective in preventing or reversing the negative inotropic effects of MDF in isolated cat papillary muscles. Column chromatography of plasma from control cats, from untreated shocked cats and from cats treated with Trasylol before shock showed six peptide peaks, designated A, B, C, D, E, and F in decreasing order of molecular weights. Peptides corresponding to peaks A, B, E, and F exhibited insignificant myocardial depressant activity. The peptide corresponding to peak C was present in control plasma and accounted for some of the small negative inotropic effect of control plasma. The peptide corresponding to peak D had a marked myocardial depressant effect which could account for all the activity of shock plasma. The molecular weight of this peptide was estimated to be 800 to 1000. This peptide is not bradykinin, but appears to be produced by a protease present in shock.