Effect of a transient period of ischemia on myocardial cells. I. Effects on cell volume regulation.

The effect of temporary periods of ischemia on the electrolytes and water of myocardial cells were studied in groups of mongrel dogs. Myocardial tissue exposed to 40 minutes of ischemia induced by occlusion of the circumflex branch of the left coronary artery developed no changes in water or electrolytes when compared to nonischemic left ventricle of the same or sham-operated animals, even though this period of ischemia is known to produce irreversible injury to many of the damaged cells. However, reperfusion of the affected myocardium with arterial blood for only 2 minutes resulted in striking increases in tissue H(2)O, Na(-), Cl(-) and Ca(2-). These changes in electrolytes increased in severity with longer periods of reflow, and tissue K(+) was decreased significantly after 10 minutes of reflow had passed. Analysis of the results suggested that the tissue edema was primarily the result of cellular swelling. Myocardium exposed to 15 minutes of ischemia followed by 2 minutes of reflow showed no significant changes aside from a slight increase in Na(+). These studies demonstrate that defects in cell volume regulation occur early in severe ischemic injury.