Duello T M, Byatt J C, Bremel R D
Endocrinology. 1986 Sep;119(3):1351-5. doi: 10.1210/endo-119-3-1351.
Bovine placental lactogen (bPL) has been isolated from bovine trophoblast and characterized as a 32 K mol wt protein which exists in three different forms which differ in their isoelectric point values and their amino acid compositions. Two of the three forms have been shown to have both bovine GH (bGH)- and bovine PRL (bPRL)-like activities equal on a molar basis to bGH and BPRL in radioreceptor assays. It has been postulated that, in sheep, PL is delivered to the maternal circulation by the migration of fetal binucleate cells from the trophoblast across the fetal-maternal boundary into the uterine epithelium. To determine whether an analogous situation exists in the cow, antibodies to bPL were used to localize bPL in bovine placentomes and to measure its concentration in fetal and maternal sera. For cytology, bPL was localized on sections of placentomes from midgestation and term bovine placentas using an indirect immunoperoxidase technique. Stained binucleate cells were demonstrated throughout the trophoblast, often in close association with the microvillous boundary which separates the trophoblast from the maternal epithelium. In cross-sections of fetal villi, binucleate cells with cytoplasmic processes extending into and through the uterine epithelium were immunostained as well as cells within the plane of the uterine epithelium in close approximation or apposition to the maternal basement membrane. RIA demonstrated bPL to be present in maternal sera in concentrations of 1-2 ng/ml and in fetal sera at 5-12 ng/ml. These data are consistent with the hypothesis that binucleate cell migration accomplishes the delivery of bPL to the maternal circulation.
牛胎盘催乳素（bPL）已从牛滋养层细胞中分离出来，其特征为一种分子量为32K的蛋白质，以三种不同形式存在，它们的等电点值和氨基酸组成有所不同。在放射受体分析中，这三种形式中的两种已被证明具有与牛生长激素（bGH）和牛催乳素（bPRL）相似的活性，在摩尔基础上与bGH和bPRL相当。据推测，在绵羊中，胎盘催乳素（PL）是通过胎儿双核细胞从滋养层迁移穿过胎儿 - 母体边界进入子宫上皮而输送到母体循环中的。为了确定牛是否存在类似情况，使用抗bPL抗体在牛胎盘小叶中定位bPL，并测量其在胎儿和母体血清中的浓度。对于细胞学研究，使用间接免疫过氧化物酶技术在妊娠中期和足月牛胎盘的胎盘小叶切片上定位bPL。在整个滋养层中都发现了染色的双核细胞，它们通常与将滋养层与母体上皮分开的微绒毛边界紧密相关。在胎儿绒毛的横切面上，细胞质突起延伸到子宫上皮并穿过子宫上皮的双核细胞以及子宫上皮平面内与母体基底膜紧密相邻或贴附的细胞都被免疫染色。放射免疫分析（RIA）表明，母体血清中bPL的浓度为1 - 2 ng/ml，胎儿血清中为5 - 12 ng/ml。这些数据与双核细胞迁移将bPL输送到母体循环的假设一致。
