Objective    To investigate the expression and distribution of leptin in pre-implantation embryo

and its effect on mouse embryo development in vitro.     Methods    Adult NIH female mice were superovulated and then mated with fertile males of the same strain. On the morning of 1st to 4th d of pregnancy

the oviduct and horn of uterus were dissected out and flushed with DMEM/F12 medium adequately. The embryos collected were subjected to the following procedures: ①Total RNA was isolated from embryos of each stage respectively and mRNA expression of leptin was detected by RT-PCR. ②Immunofluorescence staining was performed on blastocysts to analyze the expression and the distribution of leptin protein under laser confocal microscope.  ③Eight-cell embryos were cultured in medium containing leptin antibody at various concentrations to observe the formation and hatching of blastocysts.     Results    ①Leptin mRNA expression was only detected in blastocyst

and no expression was detected in embryos in other stages. Leptin protein was detected in cytoplasma

membrane of trophoblastic cell and inner cell mass

however no expression was detected in cell nucleus.  ②Leptin polyclonal antibody significantly inhibited formation of blastocysts (1∶400

P0.05) and prevented hatching of blastocysts from zona pellucida (1∶1 600

P0.05) in a dose-dependent manner.     Conclusion    The temporal expression of leptin suggests that leptin might play an important role during embryo development and implantation process in mice.