Temperature dependency of calcium-induced reperfusion injury in the isolated rat heart

The temperature dependence of Ca-induced reperfusion injury was studied in an isolated rat heart preparation. Hearts were subjected to 90 minutes of hypothermic arrest (20 degrees C) followed by 15 minutes of reperfusion at 20, 28, or 37 degrees C with a reperfusate containing various concentrations of Ca (0.1-2.55 mM). When reperfusion was started at 37 degrees C, the Ca concentration in the reperfusate significantly affected both postischemic functional recovery and creatine kinase leakage. Bell-shaped dose-response curves were observed. The optimal Ca concentration for 37 degrees C reperfusion was between 0.3 and 0.7 mM. When reperfusion was started at 20 degrees C, neither functional recovery nor creatine kinase leakage was dependent on the Ca concentration in the reperfusate. At 28 degrees C, functional recovery was not dependent on the Ca concentration, however, creatine kinase leakage was. These results indicate that Ca-induced reperfusion injury depends on the temperature of the reperfusate and that the boundary temperature of the reperfusate at which Ca-induced reperfusion injury becomes manifest seems to be near 28 degrees C.