Effect of beta-adrenoceptor blockers on sarcoplasmic reticular function and gene expression in the ischemic-reperfused heart

• Published in: The Journal of pharmacology and experimental therapeutics 2000-04, Vol.293 (1), p.15-23
• Main Authors: Temsah, R M, Dyck, C, Netticadan, T, Chapman, D, Elimban, V, Dhalla, N S
• Format: Article
• Language: English
• Subjects: Adrenergic beta-Antagonists - pharmacology; Animals; Atenolol - therapeutic use; Blotting, Northern; Blotting, Western; Calcium - metabolism; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Cyclic AMP-Dependent Protein Kinases - metabolism; Egtazic Acid - pharmacology; Gene Expression - drug effects; Male; Myocardial Contraction - drug effects; Myocardial Reperfusion Injury - drug therapy; Myocardial Reperfusion Injury - genetics; Myocardial Reperfusion Injury - physiopathology; Myocardium - metabolism; Phosphorylation; Propranolol - therapeutic use; Rats; Rats, Sprague-Dawley; RNA - isolation & purification; Sarcoplasmic Reticulum - drug effects; Sarcoplasmic Reticulum - metabolism; Sarcoplasmic Reticulum - physiology
• ISSN: 0022-3565

Although beta-adrenoceptor (beta-AR) blockers are used for the treatment of ischemic heart disease, the mechanisms of their beneficial actions have not been fully elucidated. In view of the role of sarcoplasmic reticular (SR) abnormalities in cardiac dysfunction due to ischemia-reperfusion (I/R), we examined the effects of beta-AR blockers on the I/R-induced changes in SR Ca(2+) uptake and release, as well as the protein contents and gene expression of ryanodine receptor, SR Ca(2+)-pump, phospholamban, and calsequestrin. I/R in isolated rat hearts was induced by stopping the perfusion for 30 min and then reperfusing the ischemic hearts for 60 min. Hearts were treated with or without 10 microM atenolol, a beta(1)-specific blocker, or 10 microM propranolol, a nonspecific beta-blocker, 10 min before inducing ischemia as well as during the reperfusion period. I/R depressed cardiac performance, SR Ca(2+) uptake, and Ca(2+) release activities, protein contents, as well as Ca(2+)/calmodulin-dependent protein kinase and cAMP-dependent protein kinase-mediated phosphorylations, significantly. The mRNA levels for SR Ca(2+) pump, ryanodine receptors, phospholamban, and calsequestrin were also reduced by I/R. All these changes due to I/R were partially prevented by beta-AR blocker treatment. The results indicate that the beneficial effects of beta-AR blockers on cardiac performance in the I/R hearts may be related to the prevention of changes in SR Ca(2+) uptake and release activities, protein contents, as well as Ca(2+)/calmodulin-dependent protein kinase and cAMP-dependent protein kinase phosphorylations of SR proteins. On the other hand, the protection of I/R-induced alterations in mRNA levels for SR proteins by beta-AR blockers suggests cardiac SR gene expression as a molecular site of their cardioprotective action.