Abstract: Objective: To investigate the effect of sufentanil post-conditioning on the myocardial ischemia reperfusion injury (MIRI) through extracellular regulated protein kinases (ERK1/2)-mediated p70S6K signaling pathway in the rats, and to clarify the protective effect of sufentanil post-conditioning on the MIRI of the rats. Methods: Seventy-two male SD rats were randomly divided into sham operation group, ischemia-reperfusion group (I/R group), dimethylsulfoxide group (DMSO group), PD group (an inhibitor of ERK, 20 μmol·L^-1 PD98059 was administered 15 min after the end of ischemia to the start of reperfusion), sufentanil post-conditioning group (Sufen group), Sufen+PD group. Except for sham operation group, the rats in other groups were reperfused for 2 h after 30 min-ischemia. The heart rates (HR) and mean artery pressures (MAP) of the rats in various goups were recorded immediately before ischemia (T0), 30 min of ischemia (T1), 30 min of reperfusion (T2), 60 min of reperfusion (T3), 90 min of reperfusion (T4), and 120 min (T5). The myocardial infarction area was measured at the end of reperfusion; the expression levels of p-ERK1/2 and p-p70S6K proteins in myocardium tissue were detected by Western blotting method. Results: Compared with T0, The MAP and HR of the rats in I/R, Sufen, DMSO, PD, and PD + Sufen groups at T1-T4 were decreased (P<0.05).Compared with sham operation group, the HR and MAP of the rats in other groups were increased(P<0.05). Compared with I/R group, the HR and MAP of the rats in Sufen group were increased (P<0.05).Compared with I/R group (45.67% ±10.32%), the myocardial infarct area of the rats in Sufen group (20.92% ±6.88%) was reduced (P<0.05).Compared with Sufen group, the myocardial infarction area in PD + Sufen group (42.14% ±6.73%) was increased (P<0.05). Compared with sham operation group, the expression levels of p-ERK1/2and p-p70S6K proteints in myocardium tissue of the rats in I/R group, Sufen group, and DMSO group were increased (P<0.05).Compared with I/R group, the expression levels of p-ERK1/2 and p-p70S6K in myocardium tissue of the rats in Sufen group were further increased(P<0.05).Compared with Sufen group, the expression levels of p-ERK1/2 and p-p70S6K proteins in myocardium tissue of the rats in PD+Sufen group were decreased(P<0.05). Conclusion: Sufentanil post-conditioning has the protective effect on MIRI in the rats through ERK1/2-mediated p70S6K signaling pathway. Sufentanil post-conditioning improves the cardiac function indicators and reduces the myocardial infarction area.

Key words: sufentanil, ischemia-reperfusion injury, extracellular-signal regulated kinase1/2, ribosomal protein S6 kinase, myocardial infarction