Relation between contractile function and regulatory cardiac proteins in hypertrophied hearts

Chronic beta-adrenergic stimulation in rats causes a downregulation of the phospholamban (PLB) and sarcoplasmic reticulum Ca2+-ATPase (SERCA2) protein expression by 49 and 40% respectively. However, troponin and C protein levels are unaffected. In addition, it reduces cAMP formation and thus PLB phosphorylation in hypertrophied hearts. Chronic beta-adrenergic stimulation decreases the isoproterenol-stimulated positive lusitropic and inotropic effects in papillary muscles.