title: Cardiac sympathetic stimulation increases cardiac contractility but decreases contractile efficiency in canine hearts in vivo.
abstract: The effect of cardiac sympathetic stimulation on cardiac contractile efficiency was studied in dogs. In 19 anesthetized and open-chest dogs, left ventricular (LV) pressure, LV volume, coronary blood flow and coronary venous oxygen saturation were measured simultaneously. The LV end-systolic pressure volume relations (ESPVR) and the relation between myocardial oxygen consumption (VO2)-pressure volume area (PVA) were obtained during a transient occlusion of the inferior vena cava before and after sympathetic stimulation (9V, 6 Hz, 40 sec) both with and without 50 mg/kg of 2,3-butanedione monoxime (BDM). Without BDM, sympathetic stimulation increased the slope of ESPVR by 62% (p<0.05), the slope of the VO2-PVA line by 19% (p<0.05) and the y-axis intercept of the VO2-PVA by 65% (p<0.05). With BDM, the increase in the slope of the VO2-PVA line became insignificant although other responses were similarly preserved. These data imply that cardiac sympathetic stimulation decreases cardiac contractile efficiency through mechanisms by which norepinephrine-induced beta-adrenergic activation enhances myosin ATPase-operating ATP hydrolysis in crossbridge formation.
authors.affiliation: Second Department of Internal Medicine, Hirosaki University School of Medicine, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kudo
authors.forename: A
authors.initials: A
authors.lastname: Mikuniya
authors.forename: N
authors.initials: N
authors.lastname: Suto
authors.forename: T
authors.initials: T
authors.lastname: Okubo
authors.forename: T
authors.initials: T
authors.lastname: Yamamoto
authors.forename: K
authors.initials: K
authors.lastname: Okumura
mesh_terms: D000818:Animals; D003931:Diacetyl / Q000031:analogs & derivatives / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D004562:Electrocardiography; D004734:Energy Metabolism; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*
chemical_list: C004717:diacetylmonoxime; D003931:Diacetyl