Regulation of murine myocardial energy metabolism during adrenergic stress studied by in vivo 31P NMR spectroscopy.
Image-guided, spatially localized 31P magnetic resonance spectroscopy (MRS) was used to study in vivo murine cardiac metabolism under resting and dobutamine-induced stress conditions. Intravenous dobutamine infusion (24 mug. min-1. kg body wt-1) increased the mean heart rate by approximately 39% from 482 +/- 46 per min at baseline to 669 +/- 77 per min in adult mice. The myocardial phosphocreatine (PCr)-to-ATP (PCr/ATP) ratio remained unchanged at 2.1 +/- 0.5 during dobutamine stress, compared with baseline conditions. Therefore, we conclude that a significant increase in heart rate does not result in a decline in the in vivo murine cardiac PCr/ATP ratio. These observations in very small mammals, viz., mice, at extremely high heart rates are consistent with studies in large animals demonstrating that global levels of high-energy phosphate metabolites do not regulate in vivo myocardial metabolism during physiologically relevant increases in cardiac work.
Naumova
A V
AV
Department of Radiology, Magnetic Resonance Research Division, The Johns Hopkins University School of Medicine, 217 Traylor Building, 720 Rutland Avenue, Baltimore, MD 21205, USA.
Weiss
R G
RG
Chacko
V P
VP
D000255:Adenosine Triphosphate / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001824:Body Constitution; D004280:Dobutamine / Q000494:pharmacology*; D004734:Energy Metabolism / Q000187:drug effects* / Q000502:physiology*; D006339:Heart Rate; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D009206:Myocardium / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D010759:Phosphorus Isotopes
D000318:Adrenergic beta-Agonists; D010759:Phosphorus Isotopes; D010725:Phosphocreatine; D004280:Dobutamine; D000255:Adenosine Triphosphate