Waring Dennis W, Turgeon Judith L
Division of Endocrinology, Department of Medicine, University of California, One Shields Avenue, Davis, California 95616, USA.
Endocrinology. 2006 Dec;147(12):5798-805. doi: 10.1210/en.2006-1112. Epub 2006 Aug 31.
We report the first study of voltage-activated and GnRH-induced plasma membrane currents and their modulation by estradiol (E2) in mouse gonadotrophs. In consideration of the pleiotropic effects of E2 on gonadotrophin secretion and the relationship between plasma membrane electrical excitability and secretion, our objective was to determine the role of E2 in modulating gonadotroph plasma membrane currents. We measured total voltage-activated and GnRH-induced currents using the perforated-patch configuration of the patch-clamp technique, which preserves signaling pathways, including GnRH-induced Ca2+ oscillations. We show that female mouse gonadotrophs are similar to those from other species in that the voltage-activated net current response exhibits an inward fast activating current that is inhibited by tetrodotoxin, which is characteristic of a Na+ current, and a larger magnitude outward current with a profile suggesting the presence of multiple K+ currents. Furthermore, in voltage-clamped mouse gonadotrophs, GnRH activates large amplitude current oscillations that are apamin sensitive and have a reversal potential of -90 mV, consistent with Ca2+-activated K+ currents. Significantly, E2 pretreatment for 2-5 d decreased the density of both the peak outward voltage-activated current and the peak GnRH-induced current. The specific linkage between the observed E2 effects on membrane currents and, ultimately, gonadotroph function remains to be established. However, because decreased K+ current density is associated with an increase in membrane electrical excitability, we postulate increased excitability is one of the modes of action of E2 in sensitizing the gonadotroph to GnRH, an event central to the regulation of cyclic gonadotrophin secretion.
我们报告了第一项关于小鼠促性腺激素细胞中电压激活电流和GnRH诱导的质膜电流及其受雌二醇（E2）调节的研究。鉴于E2对促性腺激素分泌具有多效性作用，且质膜电兴奋性与分泌之间存在关联，我们的目标是确定E2在调节促性腺激素细胞质膜电流中的作用。我们使用膜片钳技术的穿孔膜片配置测量了总的电压激活电流和GnRH诱导的电流，该配置保留了信号通路，包括GnRH诱导的Ca2+振荡。我们发现，雌性小鼠促性腺激素细胞与其他物种的相似，电压激活的净电流反应表现出一种内向快速激活电流，该电流被河豚毒素抑制，这是Na+电流的特征，以及一个幅度更大的外向电流，其波形表明存在多种K+电流。此外，在电压钳制的小鼠促性腺激素细胞中，GnRH激活大振幅电流振荡，该振荡对蜂毒明肽敏感，反转电位为 -90 mV，与Ca2+激活的K+电流一致。值得注意的是，E2预处理2 - 5天可降低峰值外向电压激活电流和峰值GnRH诱导电流的密度。观察到的E2对膜电流的影响与最终促性腺激素细胞功能之间的具体联系仍有待确定。然而，由于K+电流密度降低与膜电兴奋性增加相关，我们推测兴奋性增加是E2使促性腺激素细胞对GnRH敏感化的作用模式之一，这是调节周期性促性腺激素分泌的核心事件。
