title: The effects of acute and chronic beta-adrenoceptor blockade on the myofibrillar contractile system in the dog heart.
abstract: Electrophoretic and enzyme techniques have been used to study the structure and function of the contractile protein system in the myocardium of dogs before and after beta-adrenoceptor blockade. Animals were examined after acute beta-adrenoceptor blockade by using intravenous atenolol (0.2 mg/kg) and following chronic therapy with oral atenolol (100 mg twice daily) for a mean period of 106 days. Two-dimensional polyacrylamide-gel electrophoretic techniques were used to examine the myocardial contractile and regulatory proteins present in endomyocardial biopsy specimens obtained after acute and chronic beta-adrenoceptor blockade. No differences in charge, molecular weight or the relative proportions of actin, myosin light chains, tropomyosin or troponin-C were seen after either acute or chronic beta-adrenoceptor blockade. The maximal activity and calcium sensitivity of the myofibrillar adenosine triphosphatase (ATPase) was also unchanged after acute and chronic atenolol therapy. It is concluded that beta-adrenoceptor blockade has no significant adaptive effect on the structural or functional properties of the myofibril.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001262:Atenolol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D006339:Heart Rate / Q000187:drug effects; D007525:Isoelectric Focusing; D007545:Isoproterenol / Q000494:pharmacology; D009124:Muscle Proteins / Q000378:metabolism; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism; D009210:Myofibrils / Q000187:drug effects / Q000201:enzymology / Q000502:physiology
chemical_list: D009124:Muscle Proteins; D001262:Atenolol; D000251:Adenosine Triphosphatases; D007545:Isoproterenol; D002118:Calcium