Different Effects Of Gonadotropins On Rat And Mouse Oocyte Maturation In Vitro

To understand the mechanism of oocyte maturation in vitro is of great values in exploring ovary abundant oocyte resources and improving assistant reproduction techonology. As the most common used small experimental animals, rat and mouse have inconsistencys in reproduction, especially in Gondonatorpin inducing oocyte maturation.Our research was undertook to elucidate which kind of Gonadotropins play role in oocyte meiotic maturation, The effects of FSH ans LH/hCG on mouse and rat oocyte maturation in vitro were examined under different culture models.Rat Cumulus-enclosed Oocyte (CEO) and Denuded Oocyte (DO) both spontaneously resume meiotic maturation in vitro, when cultured for 2h, the germinal vesical breakdown percentage of DO reaches up to 88%, and CEOs get 53%.Oocytes begin to extrude first Polar Body 1 (FB1) when cultured for 8h. Mouse oocyte spontaneous maturation in vitro can be inhibited by 4mM Hypoxanthine (HX) or 25uM 3-Isobutyl-methylxanthine (IBMX).While, 4mM HX can not inhibit the spontaneous maturation of rat oocyte, and the lowest effective concentration of IBMX to inhibit rat oocyle spontaneous maturation in vitro is 50uM. Treated with the same concentration of IBMX, GVBD percentage of rat CEO is lower than that of DO, the results indicat that cumulus cells delay rat oocyte spontaneous maturation and potentate the inhibition effect of IBMX, but it's not the case on mouse. FSH(50U/L) can evidently induce the maturation of HX or IBMX inhibited mouse oocyte both in CEO or Follicle-enclosed Oocyte culture system., but FSH(50-200U/L) and LH (100-10,000IU/L) have little effect on rat oocyte maturation in the same culture system as mouse's in our research.RS-21607(azalanstat) is one of the specific inhibitor of CYP51 protein, which is the critical synthase of Meiosis-activating Sterol (MAS). 40-80u,M RS-21607 dose dependently inhibit rat oocyte spontaneous maturation in vitro, and 100uM RS-21607 is detrimental to rat oocyte. With the Rabbit Anti-human CYP5 I protein antibody, we found that the expression of the CYP51 protein on the PMSG-treated rat ovary is similar as PMSG and hCG treated rat ovary. Interstitial cells and theca cells have strong staining as well as the granule cells and the cumulus cells of small follicle, Oocyte and the granule cells of large follicle have no staining. The results indicate that MAS may play a role in the follicle development and rat oocyte maturation. Our findings are not consistent with Vaknin KM's (2001).