OBJECTIVETo investigate the protective effect of H2S pretreatment after cerebral schemia/reperfusion injury and its mechanisms in rats.

METHODSThe rat model of global cerebral ischemia/reperfusion injury was established by bilateral common carotid arteries occlusion combined with hemorrhagic hypotension.30 rats were randomly divided into four groups(1)sham group(n=5),in which rats received sham surgery only,with their bilateral vertebral artery and bilateral common carotid artery exposed but without ischemia treatment;(2)global cerebral ischemia/reperfusion model group(IR group,n=5),in which the global cerebral ischemia was induced by 10-min occlusion of bilateral common carotid arteries combined with hypotension;(3)H2S pretreatment group(n=15),in which H2S(12,24,48 Μmol/kg)was intraperitoneally injected before operation;(4)NaCl pretreatment group(n=5),in which the rats were intraperitoneally injected with saline 30 minutes before operation.The activities of superoxide dismutase(SOD)and the levels of malondialdeehyde(MDA)in brain were measured by spectrophotometry.Brain water content was detected.The expression of heat shock protein 70(HSP70) in the hippocampus was determined by Western blotting.

RESULTSThe SOD activities were significant increased in groups pretreated with 12Μmol/kg H2S(P=0.042),24Μmol/kg H2S(P=0.002),and 48Μmol/kg H2S(P=0.000),and the SOD activity was significantly lower in the ischemia group than in the Sham group(P=0.003).The MDA activities in the 24Μmol/kg group(P=0.026)and the 48Μmol/kg group(P=0.015)groups were significantly lower than in the IR group.The brain water content was decreased in H2S pretreatment group(24Μmol/kg and 48 Μmol/kg)compared with IR group(P=0.018,P=0.008),and it was also significantly higher in the IR group than in the sham group(P=0.009).The expression of HSP70 were decreased in H2S pretreatment group(24 Μmol/kg)compared with the IR group(P=0.000),and the expression of HSP70 were significantly higher in the IR group than in HSP70 group(P=0.000).The expression of HSP70 also significantly differed between NaCl group and HSP70 group(P=0.000).

CONCLUSIONH2S has protective effects on cerebral ischemia and reperfusion,which may be achieved by improving SOD activity,removing oxygen free radicals,inhibiting lipid peroxidation,and down-regulating the expression of HSP70 in the hippocampus.