Objective To evaluate the effect of dynein inhibitor on mouse oocyte in vitro maturation and its cyclin B1 transcription level. Methods Immature mouse oocytes were cultured in vitro with a known dynein ATPase activity inhibitor-sodium orthovanadate (SOV) to detect the changes of maturation rate, and semi-quantitative RT-PCR and single cell RT-PCR were performed to detect the changes of cyclin B1 mRNA level. Results In dose-dependent experiments, the maturation rates of oocytes were significantly different between 5 mmol/L SOV and control groups (P<0.05), and decreased with SOV increasing doses. However, the elevation of cyclin B1 mRNA level of immatured oocytes cultured for 12 h depended on SOV concentrations ranging from 50 to 500 mmol/L. In incon- tinuity exposed SOV experiments, the maturation rates of oocytes markedly reduced after the first incubation with 400 mmol/L SOV at least for 1 h and were first cultured in SOV-free medium for 4 h or 8 h before exposure to SOV (P<0.05). In time-course experiment, the opposite changes of cyclin B1 mRNA level in oocytes between SOV and control groups were observed. Conclusion Dynein inhibitor might delay oocytes meiosis process, and cause ectopic expression of cyclin B1 in oocytes. Most Oocytes incubated with SOV blocked at germinal vesicles (GV) stage or MⅠto anaphase transition due to dynein dysfunction and ectopic transcription level of cyclin B1. Objective To evaluate the effect of dynein inhibitor on mouse oocyte in vitro maturation and its cyclin B1 transcription level. Methods Immature mouse oocytes were cultured in vitro with a known dynein ATPase activity inhibitor-sodium orthovanadate (SOV) to detect the changes of maturation rate, and semi-quantitative RT-PCR were performed to detect the changes of cyclin B1 mRNA level. Results In dose-dependent experiments, the maturation rates of oocytes were significantly different between 5 mmol / L SOV and control groups ( However, the elevation of cyclin B1 mRNA level of immatured oocytes cultured for 12 h depended on SOV concentrations ranging from 50 to 500 mmol / L. In incontrolled SOV experiments, the maturation rates of oocytes markedly reduced after the first incubation with 400 mmol / L SOV at least for 1 h and were first cultured in SOV-free medium for 4 h or 8 h before exposure to SOV (P <0.05) Conclusions Dynein inhibitor might delay oocytes meiosis process, and cause ectopic expression of cyclin B1 in oocytes. Most Oocytes incubated with SOV blocked at germinal vesicles (GV) stage or M Ito anaphase transition due to dynein dysfunction and ectopic transcription level of cyclin B1.