Kagawa Hirohiko, Horiuchi Yasuhiro, Kasuga Yosuke, Kishi Takafumi
Faculty of Agriculture, University of Miyazaki, Miyazaki, Miyazaki 889-2192, Japan.
J Exp Zool A Ecol Genet Physiol. 2009 Dec 1;311(10):752-62. doi: 10.1002/jez.560.
In this study, to elucidate the mechanisms of oocyte hydration in the Japanese eel (Anguilla japonica), we examined the in vivo and in vitro morphological changes and hydration process occurring during oocyte maturation and ovulation. We also investigated the effects of the presence of ovarian follicles, aquaporin water permeability (HgCl(2)), and yolk proteolysis (bafilomycin A1) inhibitors, gap junction uncouplers (carbenoxolone and 1-octanol), a 3beta-hydroxysteroid dehydrogenase inhibitor (trilostane), and a P450 antagonist (aminoglutethimide) on oocyte hydration during in vitro oocyte maturation and ovulation. The oocytes underwent more than threefold increase in volume during maturation and ovulation, which was artificially induced by injecting salmon pituitary extracts and 17,20beta-dihydroxy-4-pregnen-3-one (DHP). Wet and dry weight measurements indicated that water accumulation during oocyte maturation is the major factor contributing to the follicular diameter increase, suggesting that follicular diameter measurements can be used as a hydration index. In the in vitro experiments, human chorionic gonadotropin (HCG) and DHP caused an increase in the diameter of follicle-enclosed oocytes but not defolliculated oocytes. Addition of HgCl(2) and bafilomycin A1 to the incubation media inhibited the HCG- and DHP-induced increase in the follicular diameter in a dose-dependent manner. Neither carbenoxolone nor 1-octanol influenced the HCG-induced increase in the follicular diameter. Trilostane and aminoglutethimide slightly but significantly inhibited HCG-induced oocyte hydration. Consequently, we concluded that ovarian follicles are essential for HCG- and DHP-induced oocyte hydration. Furthermore, aquaporin facilitates water uptake by acting as a water channel, and yolk proteolysis is essential for water influx into oocytes via osmotic mechanisms.
在本研究中，为阐明日本鳗鲡（Anguilla japonica）卵母细胞水合作用的机制，我们检测了卵母细胞成熟和排卵过程中发生的体内和体外形态变化及水合过程。我们还研究了卵巢卵泡的存在、水通道蛋白水通透性（HgCl₂）、卵黄蛋白水解（巴弗洛霉素A1）抑制剂、缝隙连接解偶联剂（羧苄青霉素和1-辛醇）、3β-羟基类固醇脱氢酶抑制剂（曲洛司坦）以及P450拮抗剂（氨鲁米特）在体外卵母细胞成熟和排卵过程中对卵母细胞水合作用的影响。在通过注射鲑鱼垂体提取物和17,20β-二羟基-4-孕烯-3-酮（DHP）人工诱导的成熟和排卵过程中，卵母细胞体积增加了三倍多。湿重和干重测量表明，卵母细胞成熟过程中的水分积累是导致卵泡直径增加的主要因素，这表明卵泡直径测量可作为水合指数。在体外实验中，人绒毛膜促性腺激素（HCG）和DHP导致有卵泡包被的卵母细胞直径增加，但对去卵泡的卵母细胞无此作用。向孵育培养基中添加HgCl₂和巴弗洛霉素A1以剂量依赖性方式抑制了HCG和DHP诱导的卵泡直径增加。羧苄青霉素和1-辛醇均未影响HCG诱导的卵泡直径增加。曲洛司坦和氨鲁米特轻微但显著地抑制了HCG诱导的卵母细胞水合作用。因此，我们得出结论，卵巢卵泡对于HCG和DHP诱导的卵母细胞水合作用至关重要。此外，水通道蛋白作为水通道促进水分吸收，卵黄蛋白水解对于水分通过渗透机制流入卵母细胞至关重要。
