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This Article Full Text Full Text (PDF) All Versions of this Article: 287/1/H54    most recent 01082.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Yamashita, D. Articles by Takaki, M. Search for Related Content PubMed PubMed Citation Articles by Yamashita, D. Articles by Takaki, M.

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

¹Department of Physiology II, Nara Medical University, Kashihara 634-8521; and ²Department 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 O₂ consumption (MVO₂) per minute (mMVO₂) without stimulation was 0.97 ± 0.14 ml O₂·min^–1·100 g LV^–1 and mean mMVO₂ with stimulation increased to 1.80 ± 0.17 ml O₂·min^–1·100 g LV^–1 in normal Tyrode solution. Mean mVO₂ (the mMVO₂ with stimulation – the mMVO₂ without stimulation) was 0.83 ± 0.12 ml O₂·min^–1·100 g LV^–1. There were no differences between mean mMVO₂ with and without stimulation in Ca²⁺-free solution. The increases in extracellular Ca²⁺ concentrations up to 14.4 mM did not affect the mMVO₂ without stimulation but significantly increased the mMVO₂ with stimulation up to 140% of control. The mMVO₂ 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 mMVO₂ to 0.27 ± 0.06 ml O₂·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 mMVO₂. Although BDM (3–5 mM) decreased the mMVO₂ 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 mMVO₂ of mouse LV slices during shortening under mechanically unloaded conditions consists of energy expenditure for total Ca²⁺ handling during excitation-contraction coupling, basal metabolism, but no residual cross-bridge cycling.

excitation-contraction coupling; basal metabolism; free shortening