Maturation of oocytes is maintained by complex procedures along with follicular genesis and is a critical step for embryonic development. Purine known as an oocyte maturation regulator is present in follicular fluid. In this study, the roles of guanosine as a strong inhibitor of GVBD and a modulator of cyclic GMP concentration in ooyctes were revealed. Denuded immature oocytes were treated with guanosine, and the maturation rates and cGMP concentration of oocytes were measured. GVBD was blocked in a concentration dependent manner by guanosine, but this effect was reversible. However, GVBD was lagged yet not significant by adenosine. Both guanosine and adenosine modified cGMP concentration in oocytes. The characteristic of the guanosine-treated oocyte was significantly higher cGMP compared with the adenosine-treated oocyes at initial time of the maturation. Based these results, guanosine may be a strong and reversible GVBD inhibitor. Although the precise mechanism of guanosine presently is unclear, the results suggest that guanosine may lead the accumulation of cGMP in oocyte cytoplasm, which in turn suppresses GVBD.

INTRODUCTION   MATERIALS AND METHODS    Animals and Oocyte Collection    Culture of Oocytes and Chemical Treatments    Measurement of cGMP Concentration    Statistical Analysis   RESULTS    Effects of Guanosine on the Denuded Oocyte Maturation    Effects of Adenosine on the Denuded Oocyte Maturation    Change of [cGMP] during Oocyte Maturation   DISCUSSION   REFERENCES

• Cheon Yong-Pil(Department of Biochemistry, College of Medicine, Hanyang University)