Endocrine Control of Mammary Secretory Function in Concurrently Lactating-Pregnant Animals

为了建立一种有效的同时泌乳妊娠小鼠的方法，进行了胚胎移植试验。将4日龄的胚胎移植到哺乳期(L)和哺乳期假妊娠（LPP）小鼠的子宫角中，并在12天后检查其维持情况。L和LPP小鼠在哺乳4 ~ 6天移植胚胎时妊娠率较高，差异无统计学意义。然而，当胚胎移植后停止哺乳刺激时，LPP小鼠的妊娠率高于L小鼠，这表明宫颈刺激可能通过黄体功能对胚胎着床和/或维持有一定的有利作用。采用RIA法测定L、LPP、LP和妊娠(P)小鼠卵巢分散黄体细胞在不同天数的体外孕酮产量。L和LPP小鼠在哺乳期早期观察到较高的孕酮产生。泌乳早期和后期的孕酮含量均较高。L和LPP小鼠血浆黄体酮浓度无显著差异。无论如何，在哺乳期小鼠的哺乳期早期通过胚胎移植可以建立并发妊娠，而不考虑宫颈刺激。但是，植入的同步性是必须解决的问题。心房插管采血方法在本研究中取得了成功。通过血浆皮质酮水平检查无压力体积和/或间隔血样的有效性。这种方法将对小鼠的生物学研究非常有用。PL小鼠的乳腺DNA比L小鼠多30%，但分泌功能（RNA/DNA、乳糖含量）明显降低。皮质醇刺激分泌活性。大鼠Nb_2淋巴瘤细胞测定血浆泌乳活性显示，LP小鼠血浆泌乳活性是L小鼠血浆泌乳活性的100倍，表明LP小鼠体内有大量胎盘泌乳循环。人们认为，lp小鼠的乳腺组织由现有细胞和新生细胞组成，对泌乳激素的反应性相对较低。需要进一步的研究来阐明这些问题。为建立泌乳乳腺组织体外培养技术进行了初步研究。少

Embryo transfer was tested in order to develop an effective method to establish concurrently lactating-pregnant(LP) mice. Four-day-old embryos were transferred into uterine horns of lactating(L) and lactating-pseudopregnant(LPP) mice at various days of lactation and checked for their maintenance at 12 days later. The high pregnancy rate was observed when embryos were transferred at 4-6 days of lactation and no significant difference existed between L and LPP mice. However, when suckling stimulus was withdrawn after embryo transfer the pregnancy rate was higher in LPP than L mice, suggesting that the cervical stimulation may exert some favorable effects on implantation and/or maintenance of embryos probably through luteal function. The in vitro production of progesterone by dispersed luteal cells taken from ovaries of L, LPP, LP and pregnant(P) mice at various days were measured by RIA. Higher production of progesterone was observed at the early stage of lactation in L and LPP mice. Pro … More gesterone production in L mice was higher during the early stage and also at the late stage of lactation. Plasma progeserone concentration did not differ between L and LPP mice.In any case, concurrent pregnancy could be established by embryo transfer at the early stage of lactation in lactating mice irrespective of cervical stimulation. however, the synchronization of implantation should be solved. A method of blood sampling by atrial cannulation was successful in this study. Validity for stressless of volumes and/or intervals of blood sampling was examined by plasma corticosterone levels. This method will be very useful for biological studies in mice. In PL mice the mammary DNA was 30 % more than in L mice but secretory function (RNA/DNA, lactose content) was markedly depressed. Cortisol administration stimulated the secretory activity. Plasma lactogenic activity measured by a rat Nb_2 lymbhoma cell assay showed 100 times of magnitude in LP than in L mice, indicating that very much placental lactogen was circulating in LP mice. It was was considered that the mammary tissues in lp mice consist of existing cells and newly developing cells and have relatively low responsiveness to lactogenic hormone(s). Further study is required to elucidate these problems. A preliminary study was carried out to establish an in vitro culture technique of lactating mammary tissues. Less