Regulation of the prolactin receptor gene expression and its application to improvement of animal

在本实验中，作者研究了催乳素受体基因在小鼠乳腺不同生殖阶段的表达调控。为了确定催乳素受体和酪蛋白mRNAs的水平，作者利用嵌合和竞争DNA构建了竞争性反转录和聚合酶链式反应。本研究的研究结果如下。(A)。在处女期和早孕期，催乳素受体基因的表达主要受催乳素、雌二醇和孕酮的控制。高浓度孕酮可抑制催乳素和雌二醇的升高作用。(B)。催乳素受体基因的表达发生在分娩前大约8小时，是乳汁生成的触发因素。在妊娠中晚期，孕酮直接抑制哺乳的启动。(C)。哺乳第5天。随着幼鼠的去势，催乳素受体的mRNA水平呈时间依赖性下降。它的水平在断奶12小时时最低，低水平一直保持到48小时。在24岁断奶时，寄养的幼崽被提供。催乳素受体mRNA水平在6小时内恢复到0小时对照组水平，酪蛋白mRNA的变化规律与催乳素受体mRNA的变化规律基本相似。如(C)所述，分别通过24小时断奶或6小时重新哺乳来评估催乳素受体mRNA的降解和合成速度。催乳素受体信使核糖核酸的合成在哺乳第1天开始活跃，酪蛋白的合成在第10天达到高峰。这两种信使核糖核酸的水平变化主要与它们的信使核糖核酸合成速率有关。

In the present experiments, the author examined the regulation of prolactin receptor gene expression at various reproductive stages of the mouse mammary gland. In order to determine the level of prolactin receptor and casein mRNAs, the author constructed the competitive reverse-transcription and polymerase chain reaction using the chimeric and competitor DNAs. The results obtained in this study were as follow. (a). The expression of the prolactin receptor gene is controlled dominantly by prolactin, estradiol and progesterone at virgin and early pregnancy. The high concentration of progesterone inhibited the increasing action of prolactin and estradiol. (b). The expression of the prolactin receptor gene occurs about 8 hr prior to parturition and is a trigger for lactogenesis. During mid to late pregnancy, progesterone inhibited directly the initiation of lactation. (c). On day 5 of lactation. the level of prolactin receptor mRNA decreased in time-dependent manner following the removal of pups. Its level was minimal at 12 hr of weaning and low levels were maintained until of 48 hr. At 24 of weaning, foster pups were supplyed. The level of prolactin receptor mRNA returned to that of the 0 hr-weaned control within 6 hr, In case of casein mRNA,the changing profile was essentially similar to that of prolactin receptor mRNA.(d). The rates of degradation and synthesis of prolactin receptor mRNA were estimated by the 24 hr-weaning or by the 6 hr-resuckling, respectively, as described in (c). The active synthesis of prolactin receptor mRNA was found on day 1 of lactation, and that of casein synthesis was on day 10 of lactation. The levels of the two mRNAs changed primarily in relation to their rates of mRNA synthesis.