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Am J Physiol Heart Circ Physiol 285: H1420-H1427, 2003. First published June 12, 2003; doi:10.1152/ajpheart.00167.2003
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Myocardial oxygenation and high-energy phosphate levels during KATP channel blockade

Jianyi Zhang, Arthur H. L. From, Kamil Ugurbil, and Robert J. Bache

Departments of Medicine, Radiology, Physiology and the Center for Magnetic Resonance Research, University of Minnesota Health Sciences Center, Minneapolis, Minnesota 55455

Submitted 23 February 2003 ; accepted in final form 26 May 2003

Inhibition of ATP-sensitive K+ (KATP) channel activity has previously been demonstrated to result in coronary vasoconstriction with decreased myocardial blood flow and loss of phosphocreatine (PCr). This study was performed to determine whether the high-energy phosphate abnormality during KATP channel blockade can be ascribed to oxygen insufficiency. Myocardial blood flow and oxygen extraction were measured in open-chest dogs during KATP channel blockade with intracoronary glibenclamide, whereas high-energy phosphates were examined with 31P magnetic resonance spectroscopy (MRS), and myocardial deoxymyoglobin (Mb-{delta}) was determined with 1H MRS. Glibenclamide resulted in a 20 ± 8% decrease of myocardial blood flow that was associated with a loss of phosphocreatine (PCr) and accumulation of inorganic phosphate. Mb-{delta} was undetectable during basal conditions but increased to 58 ± 5% of total myoglobin during glibenclamide administration. This degree of myoglobin desaturation during glibenclamide was far greater than we previously observed during a similar reduction of blood flow produced by a coronary stenosis (22% of myoglobin deoxygenated during stenosis). The findings suggest that reduction of coronary blood flow with an arterial stenosis was associated with a decrease of myocardial energy demands and that this response to hypoperfusion was inhibited by KATP channel blockade.

blood flow; myoglobin; oxygen saturation



Address for reprint requests and other correspondence: J. Zhang, Univ. of MN Health Science Center, Mayo Mail Code 508, 420 Delaware St. SE, Minneapolis, MN 55455 (E-mail: zhang047{at}umn.edu).




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