O2 consumption of mechanically unloaded contractions of mouse left ventricular myocardial slices

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 287; no. 1; pp. H54 - H62
• Main Authors: Yamashita, Daisuke, Kohzuki, Hisaharu, Kitagawa, Yutaka, Nakashima, Tamiji, Kikuta, Akio, Takaki, Miyako
• Format: Journal Article
• Language: English
• Published: United States 01.07.2004
• Subjects: Animals; Calcium - physiology; Diacetyl - administration & dosage; Diacetyl - analogs & derivatives; Diacetyl - pharmacology; Dose-Response Relationship, Drug; Drug Combinations; Energy Metabolism; Feasibility Studies; In Vitro Techniques; Indoles - pharmacology; Male; Mice; Mice, Inbred ICR; Myocardial Contraction - drug effects; Myocardial Contraction - physiology; Myocardium - metabolism; Myocardium - ultrastructure; Oxygen Consumption - drug effects; Ventricular Function, Left
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.01082.2003

1 Department of Physiology II, Nara Medical University, Kashihara 634-8521; and 2 Department of Anatomy, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan Submitted 13 November 2003 ; accepted in final form 19 February 2004 Left ventricular (LV) myocardial slices were isolated from murine hearts (300 µm thick) and were stimulated at 1 Hz without external load. Mean myocardial slice O 2 consumption (MV O 2 ) per minute (mMV O 2 ) without stimulation was 0.97 ± 0.14 ml O 2 ·min –1 ·100 g LV –1 and mean mMV O 2 with stimulation increased to 1.80 ± 0.17 ml O 2 ·min –1 ·100 g LV –1 in normal Tyrode solution. Mean mV O 2 (the mMV O 2 with stimulation – the mMV O 2 without stimulation) was 0.83 ± 0.12 ml O 2 ·min –1 ·100 g LV –1 . There were no differences between mean mMV O 2 with and without stimulation in Ca 2+ -free solution. The increases in extracellular Ca 2+ concentrations up to 14.4 mM did not affect the mMV O 2 without stimulation but significantly increased the mMV O 2 with stimulation up to 140% of control. The mMV O 2 significantly increased up to 190% of the control in a dose-dependent manner. In contrast, the shortening did not increase in a dose-dependent manner. Cyclopiazonic acid (CPA; 30 µM) significantly reduced the mMV O 2 to 0.27 ± 0.06 ml O 2 ·min –1 ·100 g LV –1 (35% of control). The combination of 5 mM 2,3-butanedione monoxime (BDM) and 30 µM CPA did not further decrease mMV O 2 . Although BDM (3–5 mM) decreased the mMV O 2 by 28–30% of control in a dose-independent manner, 3–5 mM BDM decreased shortening in a dose-dependent manner. Our results indicate that the mMV O 2 of mouse LV slices during shortening under mechanically unloaded conditions consists of energy expenditure for total Ca 2+ handling during excitation-contraction coupling, basal metabolism, but no residual cross-bridge cycling. excitation-contraction coupling; basal metabolism; free shortening Address for reprint requests and other correspondence: M. Takaki, Dept. of Physiology II, Nara Medical Univ., Kashihara 634-8521, Japan (E-mail: mtakaki{at}naramed-u.ac.jp ).