The objective of the paper was to detect HSP72 expression and HSP72 gene sequence in heat shocked mouse preimplantation embryos and the effects of different thermo conditions on hatching rates of embryos. The mouse blastocysts cultured in vitro were heat treated at 40℃ and 38℃ for 1 h, 2 h and 3 h and then recovered at 37℃ for 3 h, 2 h and 1 h, respectively, to detect their HSP72 gene expression by using RT-PCR after the total RNA extraction. The hatching rate of the blastocysts for different treated groups was recorded and the expression of HSP72 in the blastocysts was determined by Western blot. The results showed that all the groups of blastocysts, including the control, had the expression of HSP72 gene. The expression of HSP72 protein had the highest level in the embryos stressed at 38℃ for 2 h, and it was signifi cantly higher than that in the control group. The expression of HSP72 in the groups of blastocysts treated at 40℃ was not signifi cantly different from that in the control group. The embryos with induction of mild heat shock at 38℃ for 2 h, then subjected to heat shock at 40℃ for 2 h, had a signifi cant higher(P<0.05) hatching rate of 54.74% compared to 47.85% in the embryos treated directly at 40℃ for 2 h. The above results indicated that the mouse blastocysts were sensitive to heat shock and a mild heat shock induced HSP72 gene expression. Induction of HSP72 expression with mild heat shock helped embryos to tolerate more severe heat shocks.
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