Conley A J, Christenson L K, Ford S P, Christenson R K
Department of Animal and Range Sciences, North Dakota State University, Fargo 58105.
Endocrinology. 1994 Nov;135(5):2248-54. doi: 10.1210/endo.135.5.7956948.
Localized expression of cytochromes P450 17 alpha-hydroxylase (P450c17) and aromatase (P450arom) was investigated in embryonic cell layers of elongating porcine blastocysts by immunocytochemistry. Blastocysts were flushed from the uterus on day 12 of pregnancy, fixed in paraformaldehyde, embedded in paraffin, sectioned, and stained using immunogold- and peroxidase-based techniques. Staining for both P450c17 and P450arom was intense in spherical 7- to 10-mm blastocysts, but was absent in earlier stage 2- to 4-mm blastocysts and less intense or absent in later stage 20-mm and filamentous embryos. Cytochrome P450c17 was limited to the trophoblast of all blastocysts expressing the enzyme, and in spherical 7- to 10-mm blastocysts, essentially all cells of the trophoblast layer stained positively for P450c17. However, as elongation became apparent in 10-mm blastocysts, the cells of the trophoblast became flattened, and the expression of P450c17 declined particularly in those trophoblast cells adjacent to the embryonic disc where mesoderm outgrowth was occurring. In fact, two distinct populations of trophoblast cells became obvious: one that maintained P450c17 expression, and one that did not. Moreover, those trophoblast cells expressing P450c17 were less flattened than neighboring cells in which P450c17 expression was absent. These two morphologically and functionally distinct trophoblastic cell populations were most obvious in areas furthest from the embryonic disc. Cytochrome P450arom was expressed in the trophoblast as well as the hypoblast under the embryonic disc. Neither P450c17 nor P450arom appeared to be expressed in the embryonic disc or the mesoderm of the expanding blastocyst. These functional and structural changes in the embryonic cell layers of the elongating conceptus may be associated with the transient synthesis and secretion of estrogen that occur at the time of maternal recognition of pregnancy in the pig.
通过免疫细胞化学方法，研究了细胞色素P450 17α-羟化酶（P450c17）和芳香化酶（P450arom）在伸长的猪胚泡胚胎细胞层中的局部表达。在妊娠第12天从子宫冲洗出胚泡，用多聚甲醛固定，石蜡包埋，切片，并使用基于免疫金和过氧化物酶的技术进行染色。在直径7至10毫米的球形胚泡中，P450c17和P450arom的染色均强烈，但在早期2至4毫米的胚泡中不存在，而在后期20毫米的丝状胚胎中染色较弱或不存在。细胞色素P450c17局限于所有表达该酶的胚泡的滋养层，在直径7至10毫米的球形胚泡中，滋养层的基本上所有细胞对P450c17染色均呈阳性。然而，随着10毫米胚泡中伸长变得明显，滋养层细胞变得扁平，P450c17的表达下降，特别是在与发生中胚层生长的胚盘相邻的那些滋养层细胞中。事实上，两种不同的滋养层细胞群体变得明显：一种维持P450c17表达，另一种则不表达。此外，那些表达P450c17的滋养层细胞比相邻的不表达P450c17的细胞扁平程度更低。这两个形态和功能不同的滋养层细胞群体在距离胚盘最远的区域最为明显。细胞色素P450arom在滋养层以及胚盘下方的内胚层中表达。在扩张的胚泡的胚盘或中胚层中，P450c17和P450arom似乎均未表达。伸长的孕体胚胎细胞层中的这些功能和结构变化可能与猪妊娠母体识别时发生的雌激素的短暂合成和分泌有关。
