Contractile Properties of Glycerol-Extracted Muscle Bundles from the Chronically Failing Canine Heart

Abstract

Chronic congestive heart failure was induced in dogs by the surgical production of tricuspid insufficiency and pulmonary stenosis. Glycerol-extracted trabecular bundles from the right and left ventricles of these dogs developed significantly less tension than did similar preparations from the hearts of normal dogs. The maximum working capacity of the bundles from failing hearts was lower than that of bundles from normal hearts, hut the rate of hydrolysis of adenosinetriphosphate was the same as that of normal heart preparations. Since glycerol-extracted muscle bundles retain the basic contractile properties of fresh, surviving whole muscle but are free from membrane, neurohormonal, ionic and pH effects and are isolated from energy-supplying systems of muscle, defective contractility and decreased working capacity of muscle bundles from failing hearts may be appropriately ascribed to physiochemical changes in the contractile protein, actomyosin. Such alterations are undoubtedly of structural significance, and are related to the conformation changes in actomyosin which characterize the contractile cycle of muscle.