[Protective effects of high potassium administered after ischemic arrest against reperfusion injury in isolated rat hearts].

High potassium solution is one of the most commonly used cardioplegic solution, but the mechanism of action is still poorly defined. In the present study, isolated rat hearts were utilized to investigate the protective effects and mechanism of action of high potassium against ischemia/reperfusion injury. The results showed that high potassium (22 mmol/L) apparently improved the recovery of contraction amplitude (P < 0.01), inhibited the rise of resting tension (P < 0.01) and abolished ventricular fibrillation during reperfusion after global ischemia for 40 minutes. Moreover, high potassium could preserve myocardial Na+, K(+)-ATPase activity (P < 0.01) and inhibit sodium and calcium overload (P < 0.01) during reperfusion. The results indicate that small amount of high potassium solution (5 ml) administered even after ischemic arrest of rat heart has remarkable protective effects against ischemia/reperfusion injury at 37 degrees C. Its mechanism of action is at least partially by preserving Na+,K(+)-ATPase activity and inhibiting sodium and calcium overload.