Relation Between Myocardial Function and Expression of Sarcoplasmic Reticulum Ca2+-ATPase in Failing and Nonfailing Human Myocardium

Expression of sarcoplasmic reticulum (SR) Ca-ATPase was shown to be reduced in failing human myocardium. The functional relevance of this finding, however, is not known. We investigated the relation between myocardial function and protein levels of SR Ca-ATPase in nonfailing human myocardium (8 muscle strips from 4 hearts) and in myocardium from end-stage failing hearts with dilated (10 muscle strips from 9 hearts) or ischemic (7 muscle strips from 5 hearts) cardiomyopathy. Myocardial function was evaluated by the force-frequency relation in isometrically contracting muscle strip preparations (37°C, 30 to 180 min). In nonfailing myocardium, twitch tension rose with increasing rates of stimulation and was 76% higher at 120 min compared with 30 min (P