[Changes in calcium and water content of stunned myocardium and effects of hyperosmotic mannitol in rat heart].

In this study we investigated changes in myocardial electrolytes and water contents following 20 min of global ischemia and 40 min reperfusion in isolated rat hearts perfused by Langendorff procedure. After ischemia and reperfusion, calcium and water contents in myocardium increased by 42% (P less than 0.01) and 7.6% (P less than 0.05) respectively as compared with nonischemic myocardium, but sodium, potassium and magnesium in myocardial tissue did not change significantly (P greater than 0.05). When hyperosmotic mannitol (12%) was infused at the beginning of reperfusion and persisted for 25 min, postischemic left ventricular function was improved significantly. At 40 min of reperfusion, heart rate-left ventricular pressure product, an index of ventricular function, recovered to 85% of preischemia, and only 66.3% recovery was seen in postischemic heart without mannitol (P less than 0.01). In addition, hyperosmotic mannitol caused marked decreases in myocardial calcium, water and other cations, suggesting that nonspecific sarcolemmal permeability changes induced by ischemia/reperfusion probably is one of entry routes of calcium into the cell. We conclude that calcium overload with mild myocardial edema is involved in myocardial stunning and hyperosmotic mannitol can improve the function of stunned myocardium in isolated rat heart, which is, at least partially, due to the reduction of myocardial calcium overload and swelling.