title: A calcium independent on-off switch for cardiac force generators.
abstract: Developed force and ATPase activity of actomyosin in cardiac muscle are regulated not only by the concentration of cytosolic calcium, but also by the state of the contractile proteins. In this study, it has been shown that cardiac actomyosin ATPase, even in the presence of adequate Ca, can exist in an inactive state. Micromolar cyclic AMP activates the ATPase, inducing substantial enzymatic activity. Both active and inactive forms of myosin can co-exist in the same cells. Mammalian hearts appear to contain a physiological mechanism for altering the response of actomyosin to optimal concentrations of Ca.
authors.affiliation: Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia 19104-6085.
authors.forename: S
authors.initials: S
authors.lastname: Winegrad
authors.forename: A
authors.initials: A
authors.lastname: Weisberg
authors.forename: L E
authors.initials: LE
authors.lastname: Lin
authors.forename: G
authors.initials: G
authors.lastname: McClellan
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D004789:Enzyme Activation; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000502:physiology*; D009218:Myosins / Q000378:metabolism; D051381:Rats
chemical_list: D000242:Cyclic AMP; D009218:Myosins; D002118:Calcium