Effects of isoproterenol treatment of isolated perfused rat hearts on myofibrillar phosphorylation and ATPase activity.
Perfusion of isolated rat hearts with isoproterenol resulted in increases in the level of protein-bound phosphate of the myofibrils. After perfusion of the hearts with 32P, followed by SDS-polyacrylamide gel electrophoresis of the purified myofibrils, four major 32P-containing protein bands were identified. Most of the increased 32P incorporation produced by isoproterenol was localized on the troponin I and myosin light chain bands, and, to lesser extent, on the M-protein band. ATPase activity was tested in the purified myofibrils. No changes in Ca2+ requirement for activation were found after isoproterenol perfusion. However, maximal ATPase activity was markedly reduced in the myofibrils obtained from isoproterenol-treated hearts. It would appear that the myofibrillar protein phosphorylation induced by isoproterenol perfusion results in a decrease in actomyosin ATPase activity.
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D009210:Myofibrils / Q000378:metabolism; D010477:Perfusion; D010766:Phosphorylation; D051381:Rats; D011919:Rats, Inbred Strains
D009124:Muscle Proteins; D000252:Calcium-Transporting ATPases; D007545:Isoproterenol