AJP - Heart and Circulatory Physiology, Vol 267, Issue 3 894-H904, Copyright © 1994 by American Physiological Society

ARTICLES

Hyperperfusion and cardioplegia effects on myocardial high-energy phosphate distribution and energy expenditure

J. Zhang, L. Shorr, M. Yoshiyama, H. Merkle, M. Garwood, D. C. Homans, R. J. Bache, K. Ugurbil and A. H. From
Department of Medicine, University of Minnesota Health Sciences Center, Minneapolis.

This study examines the hypothesis that high-energy phosphate (HEP) compound levels in unstimulated in vivo myocardium are defined by 1) the level of perfusion and 2) non-perfusion-dependent metabolic characteristics. This hypothesis was tested by determining 1) the effects of pharmacological hyperperfusion of functioning myocardium on transmural HEP compound distribution, contractile function, and myocardial oxygen consumption rate (MVO2) as well as 2) the effect of KCl cardioplegia on transmural myocardial HEP compound distribution. Creatine phosphate (CP) and ATP were measured across the anterior left ventricular wall using spatially localized 31P-nuclear magnetic resonance (NMR). At baseline, the CP-to-ATP (CP/ATP) ratio was significantly lower in the subendocardium than in the subepicardium. This transmural HEP gradient was abolished by hyperperfusion without significant effects on contractile function or MVO2. Similarly, KCl arrest significantly increased CP and CP/ATP in all myocardial layers, and the transmural gradient of CP/ATP was abolished again. These studies indicate that in present experimental model 1) myocardial performance is not constrained by inadequate perfusion in any myocardial layer although modest oxygen limitation affects the kinetics of oxidative phosphorylation in the inner myocardial layers and 2) in all myocardial layers, submaximal activation of intermediary metabolism and oxidative phosphorylation reactions results in lower steady-state CP and higher ADP levels relative to their respective values when energy expenditure is markedly reduced by KCl arrest.

This article has been cited by other articles:

				Y. K. Cho, H. Merkle, J. Zhang, N. V. Tsekos, R. J. Bache, and K. Ugurbil Noninvasive measurements of transmural myocardial metabolites using 3-D 31P NMR spectroscopy Am J Physiol Heart Circ Physiol, January 1, 2001; 280(1): H489 - H497. [Abstract] [Full Text] [PDF]

				D. F. Torchiana, A. J. Vine, K. O. Shebani, H. L. Kantor, J. S. Titus, C.-Z. Lu, W. M. Daggett, and G. A. Geffin Cardioplegia and ischemia in the canine heart evaluated by 31P magnetic resonance spectroscopy Ann. Thorac. Surg., July 1, 2000; 70(1): 197 - 205. [Abstract] [Full Text] [PDF]

				J. Zhang, C. Toher, M. Erhard, Y. Zhang, K. Ugurbil, R. J. Bache, T. Lange, and D. C. Homans Relationships Between Myocardial Bioenergetic and Left Ventricular Function in Hearts With Volume-Overload Hypertrophy Circulation, July 1, 1997; 96(1): 334 - 343. [Abstract] [Full Text]

				J. Zhang and K. M. McDonald Bioenergetic Consequences of Left Ventricular Remodeling Circulation, August 15, 1995; 92(4): 1011 - 1019. [Abstract] [Full Text]