Habibi H R, Van der Kraak G, Bulanski E, Peter R E
Department of Zoology, University of Alberta, Edmonton, Canada.
Am J Physiol. 1988 Aug;255(2 Pt 2):R268-73. doi: 10.1152/ajpregu.1988.255.2.R268.
The effects of native and an agonist analogue of teleost gonadotropin-releasing hormone (GnRH) [(D-Arg6, Trp7, Leu8, Pro9-NHEt)-GnRH; tGnRH-A] on the hormone-induced meiotic maturation of goldfish oocytes were investigated. Incubation of follicle-enclosed goldfish oocytes with either carp gonadotropin (GtH) or meiogenic progestogens, including 17 alpha-hydroxyprogesterone (HP) and 17 alpha,20 beta-dihydroxyprogesterone (DHP), reinitiated oocyte meiosis in vitro, as indicated by germinal vesicle dissolution (GVD). Addition of tGnRH-A (10(-7) M) significantly attenuated the GVD response to GtH, HP, and DHP in a dose-related fashion; tGnRH-A reduced the magnitude of progestogen-induced GVD response without significantly affecting the sensitivity of the oocytes to the meiogenic steroids. Similarly, administration of native teleost GnRH (tGnRH) significantly attenuated GtH-induced GVD response, although the 50% maximal response of the native peptide was significantly higher than that of tGnRH-A (380.9 +/- 125 and 2.72 +/- 0.94 nM, respectively). The present results provide the first demonstration of an inhibitory action of a GnRH agonist on the process of progestogen-induced oocyte meiosis and support the hypothesis that GnRH or a GnRH-like peptide might play a modulating role in the control of oocyte meiosis at the ovarian level in goldfish.
研究了硬骨鱼促性腺激素释放激素（GnRH）的天然形式及其激动剂类似物[（D-Arg6，Trp7，Leu8，Pro9-NHEt）-GnRH；tGnRH-A]对金鱼卵母细胞激素诱导的减数分裂成熟的影响。用鲤鱼促性腺激素（GtH）或减数分裂原性孕激素（包括17α-羟基孕酮（HP）和17α，20β-二羟基孕酮（DHP））孵育卵泡包裹的金鱼卵母细胞，可在体外重新启动卵母细胞减数分裂，以生发泡溶解（GVD）为指标。添加tGnRH-A（10^-7 M）以剂量相关的方式显著减弱了对GtH、HP和DHP的GVD反应；tGnRH-A降低了孕激素诱导的GVD反应的幅度，而不显著影响卵母细胞对减数分裂甾体激素的敏感性。同样，施用天然硬骨鱼GnRH（tGnRH）显著减弱了GtH诱导的GVD反应，尽管天然肽的50%最大反应显著高于tGnRH-A（分别为380.9±125和2.72±0.94 nM）。本研究结果首次证明了GnRH激动剂对孕激素诱导的卵母细胞减数分裂过程具有抑制作用，并支持了GnRH或GnRH样肽可能在金鱼卵巢水平的卵母细胞减数分裂控制中起调节作用的假说。
