Contractile Proteins of Heart Muscle in Man

Abstract

This report deals with the contractile proteins of human muscle in congestive failure, and with the role played by the contractile proteins and by biochemical processes in the regulation of the mechanical function of the heart. The contractility of actomyosin bands prepared from heart muscle of patients who had died in congestive failure was diminished as compared to those prepared from normal hearts. This may have been the result of defective protein synthesis. The increase in heart rate was correlated with the activity of phosphorylase a in heart muscle and with changes in carbohydrate intermediates (lactate, glucose-6-phosphate [G-6-P] and glycogen). The heart rates over 300 per minute were associated with a transient increase, followed by a decrease, in phosphorylase a activity; glycogen diminished, while lactate and G-6-P increased. The oxidation-reduction potential in heart muscle became more negative. In the absence of myocardial anoxia, the increased rate of stimulation of the heart produced no alterations in either the concentration of carbohydrate intermediates or the phosphorylase a activity. Alterations in function of the heart that come into play upon rapid changes of cardiac activity are the result of the integration of several diverse biochemical cellular reactions. The contractile proteins are but following the lead of the cellular elements concerned with the production of energy.