Mishra A, Seshagiri P B
Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore-560012, India.
Mol Hum Reprod. 2000 Nov;6(11):1005-12. doi: 10.1093/molehr/6.11.1005.
The source and nature of zona lytic factors during zona escape of hamster blastocyts were investigated. When cultured in hamster embryo culture medium (HECM)-2h, all 8-cell embryos (n = 135) developed to zona escaped-blastocysts with complete zona lysis. In addition, 2-cell embryos, when co-cultured with zona escaping-blastocysts (at a ratio of 1:10), exhibited zona lysis. Various other embryos at the 1-8-cell stages also showed zona lysis when cultured with zona-escaping blastocysts. However, zonae from mice, rats, sheep and humans were resistant to lysis under these conditions. Pronase treatment resulted in rapid zona lysis in hamsters (7 +/- 1 s), whereas in other species zona lysis was much slower: mouse (662 +/- 27 s), rat (532 +/- 16 s), sheep (120 +/- 12 s) and human (104 +/- 8 s). When cysteine protease inhibitors (antipain, leupeptin, E-64 and p-hydromercuricbenzoate) were tested, they completely inhibited zona escape, while trypsin inhibitors (TLCK and SBTI) did not. Uterine zona lysin contribution in zona escape was discounted since: (i) uterine luminal flushing and endometrial extract from day 4 (the time of zona escape in vivo) pregnant females failed to lyse zonae and (ii) endogenous oocytes and transferred 2-cell embryos (to day 3 pseudopregnant recipients) were all zona-intact, while 71% of transferred blastocysts exhibited zona escape, following their recovery after 24 h. These observations suggest that a species-specific, embryonic proteolytic factor, with a cysteine protease-like activity, is involved in the zona escape of blastocysts in hamsters.
研究了仓鼠囊胚透明带逃逸过程中透明带溶解因子的来源和性质。当在仓鼠胚胎培养基（HECM）-2h中培养时，所有8细胞胚胎（n = 135）都发育成透明带逃逸囊胚，透明带完全溶解。此外，2细胞胚胎与透明带逃逸囊胚共培养（比例为1:10）时，也出现了透明带溶解。1-8细胞阶段的其他各种胚胎与透明带逃逸囊胚共培养时，也表现出透明带溶解。然而，在这些条件下，小鼠、大鼠、绵羊和人类的透明带对溶解具有抗性。蛋白酶处理导致仓鼠的透明带迅速溶解（7±1秒），而在其他物种中，透明带溶解要慢得多：小鼠（662±27秒）、大鼠（532±16秒）、绵羊（120±12秒）和人类（104±8秒）。当测试半胱氨酸蛋白酶抑制剂（抗蛋白酶、亮抑酶肽、E-64和对羟基汞苯甲酸）时，它们完全抑制了透明带逃逸，而胰蛋白酶抑制剂（甲苯磺酰-L-赖氨酸氯甲基酮和大豆胰蛋白酶抑制剂）则没有。子宫透明带溶解素对透明带逃逸的作用被排除，原因如下：（i）来自第4天（体内透明带逃逸时间）怀孕雌性的子宫腔冲洗液和子宫内膜提取物未能溶解透明带；（ii）内源性卵母细胞和移植的2细胞胚胎（移植到第3天假孕受体）的透明带均完整，而71%的移植囊胚在24小时后恢复时出现了透明带逃逸。这些观察结果表明，一种具有半胱氨酸蛋白酶样活性的物种特异性胚胎蛋白水解因子参与了仓鼠囊胚的透明带逃逸。
