Cheon M, Park D, Kim K, Park S D, Ryu K
Endocrine Laboratory, Medical Research Center, College of Medicine, Yonsei University, Seoul, South Korea.
Endocrine. 1999 Aug;11(1):49-55. doi: 10.1385/ENDO:11:1:49.
The present study examined the effects of continuous treatment with gonadotropin-releasing hormone (GnRH) on GnRH receptor (GnRH-R) mRNA levels in dispersed cultures of rat pituitary cells. Pituitary GnRH-R mRNA levels were determined by competitive reverse transcriptase polymerase chain reaction. When pituitary cells were continuously exposed to a low dose of GnRH (0.2 nM), GnRH-R mRNA levels were transiently increased. The levels of GnRH-R mRNA were significantly increased up to 6 h and diminished to untreated levels by 24 h. Luteinizing hormone (LH) release was also increased significantly up to 12 h, maintaining similar levels in LH release thereafter. When GnRH antagonist ([D-pGlu1, D-Phe2, D-Trp3,6]-LH-RH) was added to the cultures together with GnRH (0.2 nM) for 6 h, the stimulatory effect of GnRH on GnRH-R mRNA levels and LH release was significantly diminished in a dose-related manner. In another experiment, pituitary cells were treated with various doses of GnRH (0.02-200 nM) for a relatively short (6 h) or a longer (24 h) period. When pituitary cells were exposed for 6 h, all doses of GnRH (0.02-200 nM) significantly increased GnRH-R mRNA levels in a dose-dependent manner. By contrast, continuous exposure to GnRH for 24 h was ineffective in changing pituitary GnRH-R mRNA levels at any given doses. These results indicate that the duration of GnRH treatment is critical for upregulation of GnRH-R mRNA by continuous GnRH. When pituitary cells were treated for 6 h with either a continuous mode of GnRH (0.2 nM) or an hourly pulsatile mode of GnRH (0.2 nM, 6 min/h), both treatments significantly augmented GnRH-R mRNA levels. Thus, the modes of GnRH application, if treated for a relatively short period, do not appear to make a significant difference in upregulation of GnRH-R mRNA levels. Collectively, our data provide strong evidence that continuous GnRH application is able to upregulate pituitary GnRH-R mRNA levels, if treated for a relatively short period (6 h).
本研究检测了用促性腺激素释放激素（GnRH）持续处理对大鼠垂体细胞分散培养物中GnRH受体（GnRH-R）mRNA水平的影响。垂体GnRH-R mRNA水平通过竞争性逆转录聚合酶链反应来测定。当垂体细胞持续暴露于低剂量的GnRH（0.2 nM）时，GnRH-R mRNA水平短暂升高。GnRH-R mRNA水平在6小时内显著升高，并在24小时时降至未处理水平。促黄体生成素（LH）释放也在12小时内显著增加，此后LH释放维持在相似水平。当将GnRH拮抗剂（[D-焦谷氨酸1，D-苯丙氨酸2，D-色氨酸3,6]-LH-RH）与GnRH（0.2 nM）一起加入培养物中6小时时，GnRH对GnRH-R mRNA水平和LH释放的刺激作用以剂量相关的方式显著减弱。在另一项实验中，垂体细胞用不同剂量的GnRH（0.02 - 200 nM）处理相对较短（6小时）或较长（24小时）的时间。当垂体细胞暴露6小时时，所有剂量的GnRH（0.02 - 200 nM）均以剂量依赖的方式显著增加GnRH-R mRNA水平。相比之下，在任何给定剂量下，持续暴露于GnRH 24小时对改变垂体GnRH-R mRNA水平均无效。这些结果表明，GnRH处理的持续时间对于通过持续给予GnRH上调GnRH-R mRNA至关重要。当垂体细胞用持续模式的GnRH（0.2 nM）或每小时脉冲模式的GnRH（0.2 nM，6分钟/小时）处理6小时时，两种处理均显著增加GnRH-R mRNA水平。因此，如果处理时间相对较短，GnRH的应用模式似乎对GnRH-R mRNA水平的上调没有显著差异。总体而言，我们的数据提供了强有力的证据，即如果处理时间相对较短（6小时），持续给予GnRH能够上调垂体GnRH-R mRNA水平。
