Richard F J, Tsafriri A, Conti M
Division of Reproductive Biology, Department of Gynecology and Obstetrics, Stanford University School of Medicine, Stanford, California 94305-5317, USA.
Biol Reprod. 2001 Nov;65(5):1444-51. doi: 10.1095/biolreprod65.5.1444.
It is generally accepted that cyclic nucleotides are key signaling molecules in the control of oocyte meiotic resumption. Given the role of phosphodiesterases (PDEs) in cyclic nucleotide degradation, this study was undertaken to investigate the properties and regulation of PDEs expressed in rat oocytes. Cilostamide-sensitive PDE3 was the major activity detected in denuded oocytes, whereas no PDE3 activity could be detected in cumulus cells. Moreover, comparable levels of PDE3 activity were measured in cumulus-oocyte complexes (COCs) and in denuded oocytes. The oocyte PDE was recovered in the soluble fraction of the homogenate and immunoprecipitated with a specific PDE3A antibody. A significant and transient increase (P < 0.05) in PDE3 activity was measured in the oocytes after 30 min of culture (70 min after isolation) compared with immediately after collection (10 min after isolation). Conversely, no changes in activity were observed when denuded oocytes or cumulus cells were incubated for up to 130 min. Evaluation of oocyte maturation indicated that only 10% of oocytes had resumed meiosis at the peak of the PDE3 activity. A significant increase (P < 0.05) in PDE3 activity was measured in COCs when follicle-enclosed oocytes were cultured in the presence of hCG. Again, this increase preceded oocyte maturation. In conclusion, these data demonstrate that PDE3A is the major PDE form expressed in mammalian oocytes. PDE3A activity increases prior to resumption of meiosis in both spontaneous and gonadotropin-stimulated maturation. These findings strongly support the hypothesis that an increase in oocyte PDE3A activity is one of the intraoocyte mechanisms controlling resumption of meiosis in rat oocytes, at least in vitro.
一般认为，环核苷酸是控制卵母细胞减数分裂恢复的关键信号分子。鉴于磷酸二酯酶（PDEs）在环核苷酸降解中的作用，本研究旨在探讨大鼠卵母细胞中表达的PDEs的特性和调节。西洛酰胺敏感的PDE3是裸卵中检测到的主要活性酶，而在卵丘细胞中未检测到PDE3活性。此外，在卵丘-卵母细胞复合体（COCs）和裸卵中测得的PDE3活性水平相当。卵母细胞PDE存在于匀浆的可溶部分，并用特异性PDE3A抗体进行免疫沉淀。与刚采集后（分离后10分钟）相比，培养30分钟（分离后70分钟）的卵母细胞中PDE3活性显著且短暂升高（P<0.05）。相反，裸卵或卵丘细胞孵育长达130分钟时，未观察到活性变化。卵母细胞成熟评估表明，在PDE3活性峰值时，只有10%的卵母细胞恢复了减数分裂。当卵泡包裹的卵母细胞在hCG存在下培养时，COCs中PDE3活性显著升高（P<0.05）。同样，这种升高先于卵母细胞成熟。总之，这些数据表明PDE3A是哺乳动物卵母细胞中表达的主要PDE形式。在自发和促性腺激素刺激的成熟过程中，PDE3A活性在减数分裂恢复之前升高。这些发现有力地支持了这样一种假设，即卵母细胞PDE3A活性的增加是大鼠卵母细胞中控制减数分裂恢复的卵内机制之一，至少在体外是如此。
