Petrino Teresa R, Toussaint Gesulla, Lin Yu-Wai P
Barry University, School of Natural & Health Sciences, Miami Shores, Florida 33161, USA.
Reprod Biol Endocrinol. 2007 Jun 5;5:21. doi: 10.1186/1477-7827-5-21.
Activin and inhibin are glycoproteins structurally related to the transforming growth factor-beta superfamily. These peptides were first described as factors that regulate the follicle-stimulating hormone (FSH) at the pituitary level. The possible role of inhibin and activin, at the ovarian level, in mediating the stimulatory actions of a Fundulus pituitary extract (FPE) and 17alpha,20beta-dihydroprogesterone (DHP) on oocyte maturation was investigated in this study.
In vitro culture of ovarian follicles and induction of oocyte maturation were carried out in 75% Leibovitz L-15 medium. Follicles or denuded oocytes were exposed to FPE, inhibin, activin, ethanol vehicle (control group), or DHP. The competence of the follicles or denuded oocytes to respond to the hormones was assessed by scoring germinal vesicle breakdown (GVBD) used as an indication of the reinitiation of meiosis or oocyte maturation. DHP level was measured by radioimmunoassay.
Addition of FPE promoted the synthesis of DHP by the granulose cells of fully grown ovarian follicles and thus stimulated GVBD in the oocyte. Presence of porcine inhibin did not hinder the synthesis of DHP stimulated by FPE, although it did inhibit the subsequent GVBD in a dose-dependent manner, suggesting that the action of inhibin was at the oocyte level. Similarly to the findings with FPE, inhibin also blocked the DHP-induced GVBD in intact follicles, as well as the spontaneous and steroid-induced GVBD of denuded oocyte. Inhibin straightforwardly blocked the response to a low dose of DHP throughout the culture period, while higher doses of the steroid appeared to overcome the inhibitory effect especially at later times. In contrast to inhibin, recombinant human activin A significantly enhanced DHP-induced GVBD in a dose-dependent manner after 48 hr, although activin alone was not able to induce GVBD without the presence of the steroid.
Taking together with our previous studies that demonstrate the presence of activin/inhibin subunits in the ovary of F. heteroclitus, these in vitro findings indicate that inhibin and activin are local regulators in the teleost ovary and have opposing effects in modulating oocyte maturation.
激活素和抑制素是与转化生长因子-β超家族结构相关的糖蛋白。这些肽最初被描述为在垂体水平调节促卵泡激素（FSH）的因子。本研究调查了抑制素和激活素在卵巢水平上，在介导底鳉垂体提取物（FPE）和17α,20β-二氢孕酮（DHP）对卵母细胞成熟的刺激作用中可能发挥的作用。
在75%的Leibovitz L-15培养基中进行卵巢卵泡的体外培养和卵母细胞成熟的诱导。将卵泡或裸卵暴露于FPE、抑制素、激活素、乙醇载体（对照组）或DHP。通过对生发泡破裂（GVBD）进行评分来评估卵泡或裸卵对激素的反应能力，生发泡破裂用作减数分裂重新启动或卵母细胞成熟的指标。通过放射免疫测定法测量DHP水平。
添加FPE可促进完全成熟的卵巢卵泡颗粒细胞合成DHP，从而刺激卵母细胞中的GVBD。猪抑制素的存在并不阻碍FPE刺激的DHP合成，尽管它确实以剂量依赖性方式抑制随后的GVBD，这表明抑制素的作用是在卵母细胞水平。与FPE的研究结果相似，抑制素也阻断了完整卵泡中DHP诱导的GVBD，以及裸卵的自发和类固醇诱导的GVBD。抑制素在整个培养期直接阻断了对低剂量DHP的反应，而更高剂量的类固醇似乎克服了抑制作用，尤其是在后期。与抑制素相反，重组人激活素A在48小时后以剂量依赖性方式显著增强了DHP诱导的GVBD，尽管在没有类固醇的情况下激活素单独不能诱导GVBD。
结合我们之前证明异鳞底鳉卵巢中存在激活素/抑制素亚基的研究，这些体外研究结果表明，抑制素和激活素是硬骨鱼卵巢中的局部调节因子，在调节卵母细胞成熟方面具有相反的作用。
