Journal of molecular and cellular cardiology
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J. Mol. Cell. Cardiol. · Jun 1997
Effects of cromakalim and glibenclamide on myocardial high energy phosphates and intracellular pH during ischemia-reperfusion: 31P NMR studies.
ATP sensitive potassium channel (KATP) openers (e.g. cromakalim) are thought to be cardioprotective during ischemia-reperfusion, while KATP blockers (e.g. glibenclamide) may potentiate ischemia-reperfusion damage. We studied cardiac energetics and intracellular pH, by 31P magnetic resonance spectroscopy, during ischemia-reperfusion of buffer perfused, isolated rat hearts in the presence of cromakalim (10 microM) or glibenclamide (1, 10 and 50 microM). Hearts were subjected to 25 min total global ischemia at 36.5 degrees C and reperfused for 45 min. ⋯ During ischemia, intracellular ATP was depleted more rapidly in the presence of 50 microM glibenclamide and intracellular acidosis was significantly attenuated (final pH 6.3 v 5.8 for control). 50 microM glibenclamide also decreased tissue lactate content at the end of ischemia (75 +/- 3 mumol/g dry weight v 125 +/- 18 for control, P < 0.05) and this attenuation of lactate accumulation and consequent decreased intracellular acidosis may be responsible for the cardioprotection observed under these conditions. These latter effects are unlikely to be related to glibenclamide's KATP blocking activity. This study demonstrates that blocking of myocardial KATP does not potentiate ischemia-reperfusion injury and, in addition, illustrates the important role played by intracellular acidosis in myocardial ischemia-reperfusion injury.