Myocardial protection of immature rabbits with an ATP-sensitive K^+ channel opener pinacidil

Objective To investigate the effectiveness of pinacidil,an opener of ATP-sensitive K+ channels,in protecting the myocardium of immature rabbit hearts from ischemic reperfusion injury.Methods Rabbit hearts underwent 30 min of global normothermic ischemia followed by 30 min of reperfusion on the modified Langendorff apparatus.Fifty-two isolated hearts of 3 - 4 week-old immature rabbits were divided into 4 groups randomly.During ischemia,3 different cardioplegic solutions were administered intermittently by infusion every 15 min(20-25 mi each time in all groups).Group 1:control group(n = 13);group 2:Krebs-Henseleit(K-H)solution with potassium(16 mmol/L)(n = 1:3);group 3:K-H solution with potassium(16 mmol/L)and pinacidil(50 μmol/L)(n = 13);group 4:K-H solution with potassium(16 mmol/L),pinacidil(50 μmol/L)and glibenclamide(10 μmol/L)(n = 13).The pre-ischemic and post-ischemic myocardial functions were assessed by the percentage recovery of the left ventricular developed pressure(LVDP);the left ventricular end-diastolic pressure(LVEDP);both the Positive peak and negative peaks of the first derivative of the left ventricular pressures(± dp/dtmax);coronary flow;the level of creatine kinase(CK),lactic dehydrogenase(LDH)and aspartate transcarbamoylase(AST)in coronary sinus venous effluent;and by myocardial ultrastructural changes.Results Before myocardial ischemia,there were no significant differences among the four groups in any of the parameters mentioned above.Post-ischemic recovery of LVDP,LVEDP,± dp/dtmax,coronary flow,the level of CK,LDH and AST,and myocardial ultrastructural changes were better in group 3 than those in the three other groups.Conclusions As a new and effective composition,pinacidil can significantly improve myocardial protection from cardioplegia for immature rabbit hearts.