To study the effect of glucose-insulin-potassium (GIK) cocktail on cardiac myocyte death (i.e., necrosis and apoptosis) and cardiac functional recovery following myocardial ischemia/reperfusion (MI/R), and to further investigate the role of insulin in the GIK-induced cardioprotective effect.
Male Sprague-Dawley rats were subjected to 30 min myocardial ischemia followed by reperfusion for 4 h (for cardiac function and cardiomyocyte apoptosis study) or 6 h (for myocardial infarction measurement). Anesthetized rats were randomly treated with continuous infusions of saline, GIK (Glucose: 200 g/L, Insulin: 60 U/L and KCl: 60 mmol/L), GK or insulin at 4 ml.kg(-1).h(-1), beginning 5 min before reperfusion and continuing through the 4-h reperfusion. Arterial blood pressure, ECG and left ventricular pressure were monitored throughout the experiment. Myocardial DNA fragmentation and myocardial infarction were determined at the end of reperfusion.
MI/R caused significant cardiac dysfunction and myocardial death (both necrosis and strong DNA ladder formation). Compared with the vehicle treated rats, the GIK-treated rats showed protection against MI/R injury as evidenced by reduced myocardial infarction [(41.3 +/- 8.3)% vs. (54.4 +/- 10.4)% of vehicle, P < 0.05, n = 10], marked decrease of DNA fragmentation, and improved recovery of cardiac systolic/diastolic function at the end of reperfusion [left ventricular developed pressure: (94 +/- 6) mm Hg vs. (86 +/- 5) mm Hg of vehicle, P < 0.05; +LVdP/dt(max): (2 940 +/- 114) mm Hg/s vs. (2 733 +/- 132) mm Hg/s, P < 0.05; -LVdP/dt(max): (2 629 +/- 156) mm Hg/s vs. (2 463 +/- 133) mm Hg/s, P < 0.05]. Insulin exerted the similar cardioprotective effects with GIK; whereas the rats receiving GK failed to show any significant, cardioprotection against MI/R injury.
GIK exerts cardioprotective effect against postischemic myocardial injury. Insulin, mainly through its anti-apoptotic effect, plays a critical role in the GIK-elicited myocardial protection in MI/R.