Alterations of Sarcoplasmic Reticulum Proteins in Failing Human Dilated Cardiomyopathy

Background Previous studies provide considerable evidence that excitation-contraction coupling may be disturbed at the level of the sarcoplasmic reticulum (SR) in the failing human heart. Disturbed SR function may result from altered expression of calcium-handling proteins. Methods and Results Levels of SR proteins involved in calcium release (ryanodine receptor), calcium binding (calsequestrin, calreticulin), and calcium uptake (calcium ATPase, phospholamban) were measured by Western blot analysis in nonfailing human myocardium (n=7) and in end-stage failing myocardium due to dilated cardiomyopathy (n=14). The levels of the ryanodine receptor, calsequestrin, and calreticulin were not significantly different in nonfailing and failing human myocardium. Phospholamban protein levels (pentameric form) normalized per total protein were decreased by 18% in the failing myocardium (P<.05). However, phospholamban protein levels were not significantly different in failing and nonfailing myocardium when normalizatio...