Effective Expression of Prolactin Receptor Gene and its Relationship with Milk Production

1.泌乳过程中催乳素受体基因的表达在小鼠乳腺中，催乳素受体mRNA的表达水平在妊娠的前5天下降约60%，其低水平一直维持到妊娠第18天的10：00。催乳素受体mRNA的水平增加约6倍，在接下来的12小时内。高水平维持在泌乳的第0天。催乳素受体mRNA的增加是由体内和体外皮质酮的增加引起的。在去卵巢的中孕小鼠乳腺中也发现了类似的变化。结论：催乳素受体基因在临产前12 h左右表达.乳汁堆积/移去对泌乳小鼠乳腺催乳素受体基因表达的影响泌乳小鼠乳腺催乳素受体mRNA在仔鼠移去母体后12 h开始下降，18 h降至最低。让断奶24小时的小鼠喂养寄养幼仔6小时。催乳素受体mRNA的恢复在6小时的护理期。催乳素受体数量的变化与催乳素受体mRNA水平的变化呈平行关系，当乳腺泌乳量达到最大值时，催乳素受体基因的表达减慢。催乳素受体mRNA增加的乳腺中的牛奶被吸吮的幼崽。结论：控制催乳素受体基因表达的主要因素是乳腺中乳汁堆积的程度。

1. Prolactin receptor gene expression at lactogenesisIn the mouse mammary gland, the level of prolactin receptor mRNA decreased about 60% during the first 5 days of pregnancy, and its low levels were maintained until 10 : 00 on day 18 of pregnancy. The level of prolactin receptor mRNA increased about 6 folds during the next 12 h period. The high level was maintained on day zero of lactation. The increase in the prolactin receptor mRNA was caused by the increase in corticosterone in vivo and in vitro. The similar changes were found in the ovariectomized midpregnant mouse mammary gland. It is concluded that the prolactin receptor gene expresses about 12 h before the onset of parturition.2. Effect of accumulation/removal of milk on prolactin receptor gene expressionProlactin receptor mRNA in the lactating mouse mammary gland began to decrease 12 h after removal of pups from their mother and its level was the lowest at 18 h. Mice which had been weaned for 24 h were allowed to nurse foster pups for 6 h. Prolactin receptor mRNA was restored during the 6 h-nursing period. The number of prolactin receptor changed in parallel with the level of prolactin receptor mRNA.Prolactin receptor gene expression slowed when the mammary gland accumulated milk maximum. Prolactin receptor mRNA increased in the mammry gland in which milk was suckled by the pups. It is concluded that the main factor controlling the prolactin receptor gene expression is the degree of milk accumulation in the mammary gland.