Role of glycolytic products in damage to ischemic myocardium. Dissociation of adenosine triphosphate levels and recovery of function of reperfused ischemic hearts.

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Abstract
The mechanism of irreversible damage to ischemic myocardium was investigated in the perfused rat heart. The time of transition from reversible to irreversible damage to contractile function was accelerated by accumulation of glycolytic products and increases in extracellular calcium. Both of these effects were largely independent of adenine nucleotide levels in the tissue. With zero coronary flow and 1.25 mM calcium the decrease in ability of the heart to recover ventricular function with reperfusion after 30 minutes of ischemia was directly correlated with accumulation of glycolytic products (as estimated by tissue lactate) during ischemia. The extent of lactate accumulation during ischemia was varied by preperfusing the hearts for 0, 10, or 15 minutes under anoxic, high coronary flow conditions to deplete tissue glycogen prior to ischemia, and by adding lactate back to the perfusate of these hearts during the ischemic period. Recovery of ventricular function was inversely related to tissue lactate during ischemia and varied from 28 to 92%, even though there was little or no change in tissue levels of residual adenosine triphosphate. Increasing extracellular calcium accelerated the time of onset of irreversible damage with little or no change in residual adenosine triphosphate levels. At any given calcium concentration, the time-dependent declines in the ability of the heart to recover ventricular function was also largely independent of adenosine triphosphate levels. These studies suggest a major role of anaerobic glycolytic products (lactate, hydrogen ion, or NADH) in ischemic damage to the heart that is unrelated to loss of tissue adenine nucleotides. With zero or low flow ischemia, this effect may result in irreversible damage to the myocardium before adenine nucleotides are reduced to critically low levels.