Abstract: Objective To study the changes of DNA methyltransferases （DNMT） in acute repeated hypoxic mice brain. Methods Mice were randomly divided into control group (H0), hypoxia group (H1) and hypoxia for 4 runs group (H4). Real-time PCR, Western blot and methyltransferase activity assay were adopted to detect the changes of three kinds of DNMTs. Results mRNA and protein levels of DNMT3A and DNMT3B were found to be decreased in H1 and H4 （p<0.05，vs H0）. The activity of DNA methyltransferase was decreased in H4（p<0.05，vs H0 and H1）. Conclusion The changes of DNA methyltransferase may be closely related to protection of the brain in hypoxic preconditioned mice.

Key words: Hypoxic preconditioning, brain, DNA methyltransferase, mouse