Murata T, Murata E, Liu C X, Narita K, Honda K, Higuchi T
Department of Physiology, Fukui Medical University, 23-3 Shimoaizuki, Matsuoka, Fukui 910-1193, Japan.
J Endocrinol. 2000 Jul;166(1):45-52. doi: 10.1677/joe.0.1660045.
The present study was designed to investigate a possible role for ovarian steroids in the regulation of rat uterine oxytocin receptor (OTR) mRNA expression before labour. By using a competitive RT-PCR system, we have previously reported that parturition was associated with high levels of uterine OTR mRNA in all the animals examined. On the other hand, near term, some rats showed high OTR mRNA levels while others did not. We therefore examined the changes in OTR mRNA expression before and during prostaglandin F(2)(alpha) (PGF(2)(alpha))-induced parturition; a paradigm adopted to reduce the variation in the onset of parturition. Injection of PGF(2)(alpha) on day 18 of pregnancy significantly increased OTR mRNA expression in all the rats within 24 h of treatment, suggesting that the variation in OTR mRNA levels during spontaneous parturition may be due to the difference in the timing of the onset of parturition. The increase in OTR mRNA was significantly abolished by injection of the anti-oestrogen compound, tamoxifen. The stimulatory action of oestrogen on OTR mRNA expression was then examined in the presence or absence of ovarian factors. Pregnant rats were ovariectomized (OVX) or sham-operated on day 18 of pregnancy and either oestrogen or vehicle was administered 6 h after the surgical operation. Oestrogen increased OTR mRNA significantly in OVX rats 18 h after administration compared with sham-operated animals. Moreover, ovariectomy alone on day 18 of pregnancy increased OTR mRNA expression to a level which reached statistical significance 24 h after the operation. In addition, oestrogen treatment increased OTR mRNA levels in OVX virgin rats in which progesterone tubes were implanted for 1 week and removed 6 h before oestrogen injection. The stimulatory effect of oestrogen was not observed in rats in which the progesterone tubes were implanted for 1 week and not removed. These results suggest that the decline of progesterone is necessary for the expression of the stimulatory effects of oestrogen on uterine OTR mRNA.
本研究旨在探讨卵巢甾体激素在分娩前对大鼠子宫催产素受体（OTR）mRNA表达的调节作用。通过使用竞争性逆转录-聚合酶链反应（RT-PCR）系统，我们先前报道，在所有检测的动物中，分娩与子宫OTR mRNA的高水平相关。另一方面，在接近足月时，一些大鼠显示出高OTR mRNA水平，而另一些则没有。因此，我们研究了在前列腺素F2α（PGF2α）诱导分娩之前和期间OTR mRNA表达的变化；采用这种模式来减少分娩开始时间的变化。在妊娠第18天注射PGF2α可在治疗后24小时内显著增加所有大鼠的OTR mRNA表达，这表明自发分娩期间OTR mRNA水平的变化可能是由于分娩开始时间的差异。注射抗雌激素化合物他莫昔芬可显著消除OTR mRNA的增加。然后在有或没有卵巢因子的情况下研究雌激素对OTR mRNA表达的刺激作用。妊娠第18天对孕鼠进行卵巢切除术（OVX）或假手术，并在手术后6小时给予雌激素或赋形剂。与假手术动物相比，给予雌激素后18小时，OVX大鼠的OTR mRNA显著增加。此外，仅在妊娠第18天进行卵巢切除术可使OTR mRNA表达增加至术后24小时达到统计学显著水平。此外，雌激素治疗可增加植入孕酮管1周并在注射雌激素前6小时取出的OVX未孕大鼠的OTR mRNA水平。在植入孕酮管1周且未取出的大鼠中未观察到雌激素的刺激作用。这些结果表明，孕酮的下降对于雌激素对子宫OTR mRNA的刺激作用的表达是必要的。
