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Evidence for the involvement of a species-specific embryonic protease in zona escape of hamster blastocysts

Mishra, Archana and Seshagiri, PB (2000) Evidence for the involvement of a species-specific embryonic protease in zona escape of hamster blastocysts. In: Molecular Human Reproduction, 06 (11). pp. 1005-1012.

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Abstract

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 tons 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 +/- 13 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.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to European Society of Human Reproduction and Embrology.
Keywords: blastocyst;hamster;hatching;protease;zona escape.
Department/Centre: Division of Biological Sciences > Molecular Reproduction, Development & Genetics (formed by the merger of DBGL and CRBME)
Date Deposited: 17 Jul 2009 10:33
Last Modified: 19 Sep 2010 04:58
URI: http://eprints.iisc.ernet.in/id/eprint/17704

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