López-Fontana Constanza M, Maselli María E, Salicioni Ana M, Carón Rubén W
Instituto de Medicina y Biología Experimental de Cuyo (IMBECU), CONICET, CCT-Mendoza, Argentina.
Reprod Fertil Dev. 2012;24(5):704-14. doi: 10.1071/RD11160.
Lactogenesis is a very complex process highly dependent on hormonal regulation. In the present study the time-course of the inhibitory actions of progesterone on prolactin secretion, mammary gland morphology and lactogenesis from mid- to late gestation in rodents was investigated. Groups of pregnant rats were luteectomised or administered with mifepristone on Day 10, 13, 15 or 17 of gestation and decapitated 28 or 48h later. Whole-blood samples and the inguinal mammary glands were taken for determinations of hormone levels and for measurement of mammary content of casein and lactose and for tissue morphology analyses, respectively. Luteectomy or mifepristone evoked prolactin increases only after Day 17 of gestation. Mammary content of casein was increased by both treatments regardless of timing or duration. Mifepristone was less effective than luteectomy in inducing lactose production and the effect was only observed after Day 15 of gestation. Analysis of mammary gland morphology confirmed the observed effect of progesterone on lactogenesis. Both treatments triggered remarkable secretory activity in the mammary gland, even without a parallel epithelial proliferation, demonstrating that the mammary epithelium is able to synthesise milk compounds long before its full lobulo-alveolar development is achieved, provided that progesterone action is abolished. Thus, the present study demonstrates that progesterone is a potent hormonal switch for the prolactin and prolactin-like effects on mammary gland development and its milk-synthesising capacity during pregnancy, and that its inhibitory action is already evident by mid-pregnancy in rodents.
乳汁生成是一个非常复杂的过程，高度依赖激素调节。在本研究中，研究了孕酮对啮齿动物妊娠中期至晚期催乳素分泌、乳腺形态和乳汁生成的抑制作用的时间进程。将妊娠大鼠分组，在妊娠第10、13、15或17天进行黄体切除术或给予米非司酮，并在28或48小时后断头。分别采集全血样本和腹股沟乳腺，用于测定激素水平、测量乳腺中酪蛋白和乳糖的含量以及进行组织形态分析。黄体切除术或米非司酮仅在妊娠第17天后引起催乳素增加。两种处理均增加了酪蛋白的乳腺含量，与时间或持续时间无关。米非司酮在诱导乳糖产生方面比黄体切除术效果差，且仅在妊娠第15天后观察到该效果。乳腺形态分析证实了孕酮对乳汁生成的观察效果。两种处理均引发了乳腺显著的分泌活动，即使没有平行的上皮增殖，这表明只要孕酮的作用被消除，乳腺上皮在其完全小叶-腺泡发育之前就能合成乳汁成分。因此，本研究表明，孕酮是一种强有力的激素开关，可调节妊娠期间催乳素及催乳素样物质对乳腺发育及其乳汁合成能力的影响，并且其抑制作用在啮齿动物妊娠中期就已明显。
