Effect of pinacidil hyperpolarized arrest on p38 mitogen-activited protein kinase expression during myocardial ischemia-reperfusion in isolated rat hearts

Abstract

Objective To investigate the effect ofpinacidil hyperpolarizaed arrest on p38 mitogen-activited protein kinase (p38MAPK) during myocardial ischemia-reperfusion (I/R) in isolated rat hearts.Methods Fortyeight male SD rats weighting 250-300 g were randomly divided into 6 groups( n =8 each): natural arrest group (group A) ; St.Thomas group (group B) ; pinacidil hyperpolarization arrest group (group C) ;5-hydroxydecanoate (5-HD) group (group D);HMR-1098 group(group E) and 5-HD + HMR-1098 group(group F).Langendorff reperfusion model was established and K-H solution was retrogradely perfused for 15 min.In group A the hearts were arrested naturally afar perfusion was stopped; in group B St.Thomas solution was perfused; in group C pinacidil hyperpolarization solution was perfused; in the other three groups,K-H solution was perfused to isolated rat hearts for 10 min followed by 5 min 5-HD (group D) or HMR-1098(group E) or 5-HD and HMR-1098(group F) perfusion,then hyperpolarization arrest solution was given in each group.Each hearts suffered 60 min ischemia after arrest followed by 30 min K-H solution reperfusion.Coronary flow(CF),HR,left ventricular developed pressure( LVDP),left ventricular systolic pressure(LVSP) and the maximum rate of pressure rise (dp/dtmax) were measured at the end of 15 min K-H solution perfusion and at 20 min of reperfusion.Myocardial phosphatic and nonphosphatic p38MAPK expression was determined by Western blot at 30 min of reperfusion.Results Compared with group C,CF,HR,LVDP,LVSP and dp/dtmax were significantly decreased at 20 min of reperfusion and phosphatic p38MAPK expression was down-regulated,non-phosphatic p38MAPK expression was up-regulated at 30 min of reperfusion in groups A,B,D,E and F (P ＜ 0.05).Compared with group E,CF,HR,LVDP,LVSP and dp/ dtmax were significantly decreased at 20 min of reperfusion and phosphatic p38MAPK expression was down-regulated,non-phosphatic p38MAPK expression was up-regulated at 30 min of reperfusion in groups D and F ( P ＜0.05).Conclusion Hyperpolarized arrest induced by pinacidil can improve cardiac function following myocardial I/R injury by up-regulating phosphatic p38MAPK expression,down-regulating non-phosphatic p38 MAPK expression and mitochondrial potassium channel is more important than membranous one during the regulation of phosphatic p38MAPK expression. Key words: Pinacidil; Heart arrest; p38Mitogen-activated protein kinases; Myocardial reperfusion