Park-Sarge O K, Parmer T G, Gu Y, Gibori G
Department of Physiology, University of Kentucky, Lexington 40536.
Endocrinology. 1995 Apr;136(4):1537-43. doi: 10.1210/endo.136.4.7534703.
To determine whether the progesterone receptor (PR) gene is expressed in rat corpora lutea (CL), PR messenger RNA (mRNA) and protein levels were examined in CL of both cycling and pregnant rats using in situ hybridization, reverse transcription-polymerase chain reaction, and Western blotting analyses. During the estrous cycle, levels of luteal PR mRNA were below the sensitivity of in situ hybridization. Although no signal could be detected in luteal cells, granulosa cells of preovulatory follicles of the same ovary expressed PR mRNA at high levels during the evening of proestrus. Likewise, CL of pregnant rats expressed undetectable levels of PR mRNA, which remained unchanged throughout pregnancy, as determined by in situ hybridization and reverse transcription-polymerase chain reaction. In addition, no PR protein could be detected in rat CL by Western analysis, indicating that luteal expression of the PR gene, if any, is negligible. To determine whether the lack of PR mRNA in the rat CL is due to progesterone-induced down-regulation of PR mRNA or to low levels of estrogen, aminoglutethimide was used to block the synthesis of progesterone in the presence and absence of exogenous estrogen, and PR mRNA levels were examined in the CL as well as the placenta. Inhibition of progesterone synthesis did increase PR mRNA levels in the placenta, and additional estrogen treatment further increased PR mRNA levels in this tissue. In contrast, neither aminoglutethimide alone nor aminoglutethimide plus estrogen induced PR mRNA expression in CL of the same rats. The temperature-sensitive luteal cell line derived from the rat CL, which produces very low levels of progesterone, also did not express PR mRNA. These results indicate that the rat corpus luteum expresses undetectable levels of PR mRNA and protein, which is not attributable to progesterone-induced down-regulation of PR mRNA or to a lack of estrogen-induced up-regulation of PR mRNA in this tissue.
为了确定孕酮受体（PR）基因是否在大鼠黄体（CL）中表达，利用原位杂交、逆转录-聚合酶链反应和蛋白质免疫印迹分析，检测了动情周期和妊娠大鼠CL中的PR信使核糖核酸（mRNA）和蛋白质水平。在动情周期中，黄体PR mRNA水平低于原位杂交的检测灵敏度。尽管在黄体细胞中未检测到信号，但在动情前期傍晚，同一卵巢排卵前卵泡的颗粒细胞高水平表达PR mRNA。同样，通过原位杂交和逆转录-聚合酶链反应确定，妊娠大鼠的CL表达不可检测水平的PR mRNA，且在整个妊娠期间保持不变。此外，通过蛋白质免疫印迹分析在大鼠CL中未检测到PR蛋白，表明PR基因在黄体中的表达（如果有的话）可忽略不计。为了确定大鼠CL中PR mRNA的缺乏是由于孕酮诱导的PR mRNA下调还是雌激素水平低，在存在和不存在外源性雌激素的情况下，使用氨鲁米特阻断孕酮的合成，并检测CL和胎盘中的PR mRNA水平。抑制孕酮合成确实增加了胎盘中的PR mRNA水平，额外的雌激素处理进一步增加了该组织中的PR mRNA水平。相比之下，单独使用氨鲁米特或氨鲁米特加雌激素均未诱导同一大鼠CL中PR mRNA的表达。源自大鼠CL的温度敏感黄体细胞系产生极低水平的孕酮，也不表达PR mRNA。这些结果表明，大鼠黄体表达不可检测水平的PR mRNA和蛋白质，这并非归因于孕酮诱导的PR mRNA下调或该组织中雌激素诱导的PR mRNA上调不足。
