ABSTRACT
Objective To evaluate the role of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38MAPK) signaling pathways in reduction of ischemia-reperfusion (I/R) injury by morphine preconditioning in the rats with heart failure.Methods Adult male Sprague-Dawley rats,weighing 200-230 g,in which doxorubicin 2 mg/kg was injected via the tail vein once a week for 6 consecutive weeks to induce chronic heart failure,were studied.At the end of 8th week,45 rats with chronic heart failure were randomly divided into 5 groups (n =9 each) using a random number table:sham operation group (group S),group I/R,morphine preconditioning group (group MPC),SP600125 (JNK inhibitor) + morphine preconditioning group (group MSP) and SB203580 (p38MAPK inhibitor) + morphine preconditioning group (group MSB).Myocardial I/R was induced by 30 min occlusion of the anterior descending branch of the coronary artery followed by 120 min reperfusion in each group except group S.In group MPC,the rats were subjected to 3 cycles of 5-min infusion of 0.1 mg/kg morphine via the femoral vein at 5 min interval before ischemia.In MSP and MSB groups,SP600125 0.5 mg/kg and SB203580 0.2 mg/kg were injected via the femoral vein,respectively,at 10 min before morphine preconditioning.The animals were sacrificed at 120 min of reperfusion,and the myocardial specimens were obtained for determination of the total areas of right and left ventricles (LV+RV),area at risk (AAR),infarct size (IS),and expression of PKC δ in myocardial tissues (by immunohistochemistry),and IS/AAR ratio was calculated.Results There was no significant difference in LV+RV and AAR between the five groups (P＞0.05).Compared with group S,IS and IS/AAR were significantly increased,and the expression of PKC δ was upregulated in I/R and MSB groups (P＜0.05).Compared with group I/R,IS and IS/AAR were significantly decreased,and the expression of PKC δ was down-regulated in MPC and MSP groups (P＜0.05).Compared with group MPC,IS and IS/AAR were significantly increased,and the expression of PKC δ was upregulated in group MSB (P＜0.05),and no significant change was found in the parameters mentioned above in group MSP (P＞0.05).Conclusion Activation of p38MAPK signaling pathway is involved in reduction of myocardial I/R injury by morphine preconditioning,and the mechanism is related to down-regulation of PKC δ expression in rats with heart failure;JNK signaling pathway is not involved in this process.
ABSTRACT
Objective To investigate the effect of different duration skeletal muscle denervation on acetylcholine receptor activity in rats.Methods Fourteen Balb/c mice weighing 18-22 g were used in this study.The denervation model was established by excising sciatic nerve.Two rats were chosen before(T0 ) and at days 1,4,7,14,21 and 28 after excising sciatic nerve (T1～6),and flexor digitorum brevis of the hindfoot was acutely isolated Skeletal muscle cells were isolated ( five cells in each rat),the acetylcholine currents were recorded using whole-cell patch-clamo technique.Extracellular fluid containing 30 μmol/L acetylcholine was first applied to skeletal muscle cells for 10 s,acetylcholine currents (11)were recorded,then the ceils were washed out using extracellularfluid.Skeletal muscle cells were balanced using extracellular fluid containing 0,0.1,1,10,30,100,1000,3000,or 10 000 nmol/L atracurium for 3 min respectively,then perfused using extracellular fluid containing 30 μmol/L acetylcholine and differents concentrations of atracurium mentioned above for 10 s respectively,and acetylcholine currents were recorded,then the cells were washed out,and 30 μmol/L acetylcholine was perfused again and currents(I2 ) were recorded.The mean value of I1 and I2 was taken as control current,and inhibitory percentage of control current was calculated,and the inhibition concentrations for the half-maximal response (IC50) of atracurium were determined by nonlinear regression analysis.Results Compared with T0,IC50 significantly increased at T1～6 ( P ＜ 0.05).IC50 was increased gradually at T1～3 ( P ＜ 0.05).Compared with T3,IC50 was decreased at T4～6 ( P ＜ 0.05).IC50 was decreased gradually at T4～6 ( P ＜ 0.05 ).Conclusion Skeletal muscle denervation can inhibite acetylcholine receptor activity,which is relate to the denervation time.