Ca(2+)-transporting ATPase, phospholamban, and calsequestrin levels in nonfailing and failing human myocardium.

Observations of abnormalities in the diastolic components of intracellular Ca2+ transients in failing human left ventricular myocardium have raised the possibility that reductions in the level or function of sarcoplasmic reticulum proteins involved in Ca2+ transport contribute to the pathophysiology of dilated cardiomyopathy in humans. Functional assays, however, have revealed no differences in ATP-dependent Ca2+ transport or its modulation by phospholamban in sarcoplasmic reticulum-enriched microsomes prepared from nonfailing and failing human left ventricular myocardium. The purpose of the present study was to quantify protein levels of Ca(2+)-transporting ATPase, phospholamban, and calsequestrin directly in nonfailing and failing human left ventricular myocardium.