Stith B J, Maller J L
Dev Biol. 1984 Mar;102(1):79-89. doi: 10.1016/0012-1606(84)90176-3.
Both insulin and progesterone are capable of stimulating germinal vesicle breakdown (GVBD) of large, Stage VI oocytes of Xenopus laevis. Numerous studies have shown an increase in intracellular pH (pHi) and ribosomal protein S6 phosphorylation prior to GVBD in oocytes treated with progesterone. In this study the effect of insulin and progesterone on pHi and S6 phosphorylation was compared. Both hormones increased pHi and S6 phosphorylation to similar levels and the time course of pHi change was the same for both hormones. Half-maximal effects of insulin were observed at 7 X 10(-8) M concentrations. In the presence of 1 nM cholera toxin, the ability of progesterone to induce these two responses was inhibited while the action of insulin was unaffected. However, GVBD induced by either hormone was blocked by cholera toxin. In small, Stage IV oocytes that do not undergo GVBD in response to either progesterone or insulin, a partial increase in pHi without S6 phosphorylation occurred in response to progesterone but both events occurred in response to insulin. These results suggest that the inability of Stage IV oocytes to undergo GVBD in response to hormone is not due to a failure to increase pHi or phosphorylate S6. The results in this paper also indicate that these events are regulated differently by insulin and progesterone in Xenopus oocytes.
胰岛素和孕酮都能够刺激非洲爪蟾大型VI期卵母细胞的生发泡破裂（GVBD）。大量研究表明，在用孕酮处理的卵母细胞中，生发泡破裂之前细胞内pH值（pHi）升高，核糖体蛋白S6磷酸化增加。在本研究中，比较了胰岛素和孕酮对pHi和S6磷酸化的影响。两种激素均将pHi和S6磷酸化提高到相似水平，且两种激素引起的pHi变化的时间进程相同。胰岛素在7×10⁻⁸ M浓度时观察到半数最大效应。在存在1 nM霍乱毒素的情况下，孕酮诱导这两种反应的能力受到抑制，而胰岛素的作用不受影响。然而，两种激素诱导的GVBD均被霍乱毒素阻断。在对孕酮或胰岛素均无反应而不发生GVBD的小型IV期卵母细胞中，孕酮可引起pHi部分升高但无S6磷酸化，而胰岛素则可引起这两种变化。这些结果表明，IV期卵母细胞对激素无反应而不能发生GVBD并非由于未能升高pHi或使S6磷酸化。本文的结果还表明，在非洲爪蟾卵母细胞中，胰岛素和孕酮对这些事件的调节方式不同。
