ABSTRACT
Aim To observe the role of ERK signaling protein in morphine preconditioning reducing global ischemia-reperfusion injury in isolated rat hearts.Methods Adult male Sprague-Dawley rats were distributed into six groups (n =10 for each) using a random number table:control group (CON),ischemia-reperfusion group (I/R),ischemia preconditioning group (IPC),morphine preconditioning group at the concentration of 1 μmol · L-1 (MPC),ERK inhibitor PD98059 + MPC (MPD),and group of ERK inhibitor-PD98059 (PD).The isolated rat hearts were treated on a Langendorff perfusion apparatus system.The coronary effluent was collected at 15 min of equilibration (baseline),5 and 10 min of reperfusion for detection of the activity of LDH.Meanwhile,a water-filled balloon was inserted into the left ventricular for continuous LVDP measurement.The IS and AAR and IS/AAR ratios were observed by TTC.Western blot was used to examine the level of phosphorylated ERK in myocardium.Results As compared with the I/R group,MPC significantly decreased IS and IS/AAR ratio as well as LDH activities at 5 min and 10 min of reperfusion,but improved the LVDP at the end of reperfusion.Moreover,the phosphorylation level of ERK in myocardium was up-regulated by MPC.However,ERK inhibitor PD98059 could block the protective effects of MPC,as indicated by the increased IS and IS/AAR ratio,elevated LDH activity at the reperfusion of 5 and 10 min,and the suppressed LVDP at the end of reperfusion.Furthermore,the MPC-induced phosphorylation of ERK was also reversed by PD98059.Conclusion Morphine preconditioning may confer cardio-protection against the global ischemia-reperfusion injury in rat hearts through enhancing the phosphorylation of ERK.