Strömstedt M, Keeney D S, Waterman M R, Paria B C, Conley A J, Dey S K
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
Mol Reprod Dev. 1996 Apr;43(4):428-36. doi: 10.1002/(SICI)1098-2795(199604)43:4<428::AID-MRD4>3.0.CO;2-R.
Implantation is initiated on day 4 in the mouse and on day 13 in the pig. The preimplantation pig blastocyst synthesizes steroid hormones, but whether preimplantation rodent embryos also have this ability has remained unresolved for the last two decades. In this study, the mRNAs encoding NADPH-cytochrome P450 reductase (P450-reductase), adrenodoxin, lanosterol 14-demethylase P450 (CYP51), 17 alpha-hydroxylase P450 (CYP17), cholesterol side-chain cleavage P450 (CYP11A1), sterol 27-hydroxylase P450 (CYP27), and aromatase P450 (CYP19) were examined in day 4 mouse blastocysts (day 1 = vaginal plug) and in day 13 and 16 pig blastocysts using reverse transcription-polymerase chain reaction (RT-PCR). In mouse blastocysts, mRNAs of P450-reductase, adrenodoxin, and CYP51, but not CYP17, CYP11A1, CYP27, and CYP19, were detected. In agreement with this finding, no aromatase protein could be detected by immunohistochemistry. By contrast, all these mRNAs were detected in the pig blastocyst. Furthermore, both the ovarian and placental types of aromatase (CYP19) mRNAs were detected in the pig blastocyst on days 13 and 16 of pregnancy, although the ovarian form was more abundant. Both forms of aromatase were much higher in day 13 than in day 16 pig blastocysts. The results provide definitive evidence that the preimplantation mouse blastocyst, as opposed to the pig blastocyst, has no ability to synthesize estrogen and no steroidogenic capacity. Maternal estrogen synthesis is essential for implantation of the mouse blastocyst.
小鼠在第4天开始着床，猪在第13天开始着床。着床前的猪囊胚能合成甾体激素，但在过去二十年里，着床前的啮齿动物胚胎是否也有这种能力一直没有定论。在本研究中，利用逆转录聚合酶链反应（RT-PCR）检测了编码NADPH-细胞色素P450还原酶（P450还原酶）、肾上腺皮质铁氧化还原蛋白、羊毛甾醇14-脱甲基酶P450（CYP51）、17α-羟化酶P450（CYP17）、胆固醇侧链裂解酶P450（CYP11A1）、甾醇27-羟化酶P450（CYP27）和芳香化酶P450（CYP19）的mRNA在第4天的小鼠囊胚（第1天=阴道栓）以及第13天和第16天的猪囊胚中的表达情况。在小鼠囊胚中，检测到了P450还原酶、肾上腺皮质铁氧化还原蛋白和CYP51的mRNA，但未检测到CYP17、CYP11A1、CYP27和CYP19的mRNA。与此发现一致，免疫组化未检测到芳香化酶蛋白。相比之下，在猪囊胚中检测到了所有这些mRNA。此外，在妊娠第13天和第16天的猪囊胚中检测到了卵巢型和胎盘型芳香化酶（CYP19）的mRNA，尽管卵巢型更为丰富。两种形式的芳香化酶在第13天的猪囊胚中都比在第16天的猪囊胚中高得多。结果提供了确凿的证据，即着床前的小鼠囊胚与猪囊胚不同，没有合成雌激素的能力，也没有甾体生成能力。母体雌激素合成对于小鼠囊胚的着床至关重要。
