Porter T E, Frawley L S
Department of Anatomy and Cell Biology, Medical University of South Carolina, Charleston 29425.
Endocrinology. 1991 Nov;129(5):2707-13. doi: 10.1210/endo-129-5-2707.
We have previously reported that the normal expression of PRL-secreting cells in neonatal rats requires a maternal signal specific to the first few days of lactation. These results raised the possibility that a milk-borne factor(s) ingested by the neonate and absorbed into the circulation might induce the ontogenic appearance of PRL cells. The purpose of the present study was to determine whether milk from this period could directly stimulate the differentiation of PRL secretors in culture. Monodispersed anterior pituitary cells from 1-day-old pups were cultured for 6 days with aqueous extracts of milk from early (days 2, 3, and 4) and late (days 15 and 16) lactation and then subjected to reverse hemolytic plaque assays for PRL and GH release. We found that the addition of milk extracts (10 mg/ml) from either early or late lactation stimulated the differentiation of PRL secretors (to 6.1 +/- 1.0% and 2.4 +/- 0.7% of all pituitary cells, respectively; mean +/- SE; n = 3) above that in control cultures without milk (0.2 +/- 0.2%). Thus, early milk was more than twice as effective as late milk in this regard (P less than 0.05). This effect appeared to be specific to PRL cell differentiation, since the relative abundance of GH secretors was not different between cells treated with either early or late milk (29.3 +/- 4.8% and 33.7 +/- 3.9%, respectively). On the other hand, late milk was more than twice as effective as early milk at increasing the capacity of GH secretors to release hormone (P less than 0.05). Preliminary characterization by gel filtration chromatography and proteolytic hydrolysis indicates that the bioactivity that differentiates PRL secretors is a small peptide(s) of 2000-6000 daltons. Taken together, our results demonstrate that a milk-borne peptide(s) is capable of specifically stimulating the differentiation of PRL-secreting cells in vitro, and that this bioactivity is more prevalent in milk from early lactation.
我们之前曾报道，新生大鼠催乳素分泌细胞的正常表达需要泌乳最初几天特有的母体信号。这些结果提出了一种可能性，即新生儿摄入并吸收进入循环的一种或多种乳源性因子可能诱导催乳素细胞的个体发育出现。本研究的目的是确定这一时期的乳汁是否能在培养中直接刺激催乳素分泌细胞的分化。将1日龄幼鼠的分散垂体前叶细胞与泌乳早期（第2、3和4天）和晚期（第15和16天）的乳汁水提取物培养6天，然后进行催乳素和生长激素释放的反向溶血空斑测定。我们发现，添加早期或晚期泌乳的乳汁提取物（10 mg/ml）均能刺激催乳素分泌细胞的分化（分别占所有垂体细胞的6.1±1.0%和2.4±0.7%；平均值±标准误；n = 3），高于无乳汁的对照培养物（0.2±0.2%）。因此，在这方面早期乳汁的效果是晚期乳汁的两倍多（P < 0.05）。这种作用似乎对催乳素细胞分化具有特异性，因为用早期或晚期乳汁处理的细胞中生长激素分泌细胞的相对丰度没有差异（分别为29.3±4.8%和33.7±3.9%）。另一方面，晚期乳汁在增加生长激素分泌细胞释放激素的能力方面比早期乳汁有效两倍多（P < 0.05）。通过凝胶过滤色谱和蛋白水解初步表征表明，使催乳素分泌细胞分化的生物活性是一种2000 - 6000道尔顿的小肽。综上所述，我们的结果表明，一种乳源性肽能够在体外特异性刺激催乳素分泌细胞的分化，并且这种生物活性在早期泌乳的乳汁中更为普遍。
