Abstract:

To explore the effect of hyperbaric oxygen（HBO） on brain tissue of rats suffered transient middle cerebral artery occlusion （MCAO） and  the Mcl-1 expression in brain cortex,and to demonstrate its mechanism. Methods 20 healthy male Wistar rats were chosen and separated randomly to  sham group(n=6),MCAO group(n=7) and  HBO group(n=7).The MCAO models were established by nylon strand method.In sham group,the blood vessels were dissected and the strand was not inserted to middle artery；the rats in MCAO group were reperfused after 90 min ischemia,and the rats in HBO group were given pure oxygen at 3.0 atmospheres absolute (ATA) for 60 min after 3 h  reperfusion.24 h after reperfusion,all the rats were killed.The infarct area of coronal brain section was calculated with 2,3,5-triphenyltetrazolium chloride (TTC) staining;the expressions of Mcl-1 mRNA and protein in cortex of penumbra were detected by RT-PCR and Western blotting,respectively.Results  Compared with MCAO group,the infarct area  ratio of the rats in HBO group was increased obviously （P<0.01）.Compared with sham group, the Mcl-1 mRNA level in brain tissue of the rats in MCAO group was up-regulated notably（P<0.01）.Compared with MCAO group,the Mcl-1 mRNA level in brain tissue of the rats  in HBO group was raised significantly（P<0.01）. Compared with sham group,the Mcl-1 protein contents in brain tissue of the rats in MCAO and HBO groups were  decreased significantly （P<0.01）;but there were no statistically significant differences（P>0.05）.Compared with MCAO group,the Bax
/Mcl-1 levels in HBO group were increased significantly （P<0.01）.Conclusion
HBO may promote the damage of MCAO rats through increasing the degradation of Mcl-1.

Key words: hyperbaric oxygen;middle cerebral artery occlusion;marginal zone myeloid cell leukemin-1, apoptosis