Goff Alan K, Jamshidi Ahmad A, Kombé Aimé
Centre de Recherche en Reproduction Animale, Faculté de médecine vétérinaire, Université de Montréal, 3200 Rue Sicotte, St-Hyacinthe, Québec J2S 7C6, Canada.
Steroids. 2006 Sep;71(9):785-91. doi: 10.1016/j.steroids.2006.05.007. Epub 2006 Jun 22.
Oxytocin receptor (OTR) expression is suppressed by progesterone (P4) during the luteal phase of the estrous cycle and then it increases at the time of luteolysis, but its regulation is still not completely understood. In vitro studies to determine the mechanism of action are hindered because OTR spontaneously upregulates in vitro and it is impossible to alter expression with P4 or estradiol. During recent studies examining the effect of P4 and an antagonist (mifepristone) on PG secretion, we found that mifepristone attenuated OT-stimulated PG secretion from endometrial epithelial cells. The objective of the present study was to determine, whether this effect of mifepristone was due to changes in prostaglandin synthesis and/or OTR. A time-course showed that mifepristone (5 microM) had no significant effect after 24 h but by 72 h it decreased PGF(2alpha) secretion (P<0.01) and abolished the response of the cells to OT (P<0.01). The presence or absence of P4 did not affect the response to mifepristone. To determine the site of action of mifepristone, cells were cultured for 72 h with or without mifepristone and then COX-1 and COX-2 were measured by Western blotting and OTR was measured by saturation analysis. The results showed that mifepristone did not affect basal or PMA-stimulated expression of either COX-1 or COX-2 but did, however, decrease OTR number (P<0.05). These data demonstrate that OTR and the response to OT can be downregulated in endometrial epithelial cells in vitro via a mechanism involving the P4 receptor.
在发情周期的黄体期，孕酮（P4）会抑制催产素受体（OTR）的表达，然后在黄体溶解时其表达增加，但其调节机制仍未完全明了。由于OTR在体外会自发上调，且无法用P4或雌二醇改变其表达，因此阻碍了确定其作用机制的体外研究。在最近一项研究P4和拮抗剂（米非司酮）对PG分泌影响的实验中，我们发现米非司酮可减弱OT刺激的子宫内膜上皮细胞PG分泌。本研究的目的是确定米非司酮的这种作用是否归因于前列腺素合成和/或OTR的变化。时间进程显示，米非司酮（5 microM）在24小时后无显著影响，但到72小时时它降低了PGF(2α)分泌（P<0.01）并消除了细胞对OT的反应（P<0.01）。P4的存在与否不影响对米非司酮的反应。为了确定米非司酮的作用位点，将细胞在有或无米非司酮的情况下培养72小时，然后通过蛋白质印迹法测量COX-1和COX-2，并通过饱和分析测量OTR。结果显示，米非司酮不影响COX-1或COX-2的基础表达或PMA刺激的表达，但确实降低了OTR数量（P<0.05）。这些数据表明，体外子宫内膜上皮细胞中的OTR和对OT的反应可通过涉及P4受体的机制下调。
