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This Article Full Text Full Text (PDF) All Versions of this Article: 71/1/291    most recent biolreprod.103.022152v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ozawa, M. Articles by Kanai, Y. Search for Related Content PubMed PubMed Citation Articles by Ozawa, M. Articles by Kanai, Y. Agricola Articles by Ozawa, M. Articles by Kanai, Y.

Redox Status of the Oviduct and Cdc2 Activity in 2-Cell Stage Embryos in Heat-Stressed Mice¹

Institute of Agriculture and Forestry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan

Mammalian preimplantation embryos are vulnerable to heat stress. However, the mechanisms by which maternal heat stress compromises embryonic development are unclear. We hypothesized that the loss of developmental competence in maternally heat-stressed embryos results from enhanced oxidative stress in the oviducts. In experiment 1, oviducts and zygotes were collected from mice that were heat-stressed at 35°C and 60% relative humidity for 12 h on the day of pregnancy as well as from control mice. The zygotes were cultured for 84 h to assess their development, and the H₂O₂ level, glutathione concentration, and free radical scavenging activity (FRSA) were measured in the oviduct. In experiment 2, zygotes were cultured for 22 h to reach the late G₂ phase in the 2-cell stage, and Cdc2 activity was assessed using immunoblotting. A high percentage (87.6%) of control embryos developed to morulae or blastocysts, whereas the majority (67.4%) of the heat-stressed group arrested at the 2-cell stage. Although heat stress did not alter the FRSA or glutathione concentration in the oviducts, the H₂O₂ level (P < 0.01) and its ratio to the FRSA (P < 0.05) significantly increased in the heat-stressed group. The Cdc2 activation at the 2-cell stage, as shown by the ratio of the dephosphorylated form to the phosphorylated form, was evident in control embryos but absent in heat-stressed embryos, and the level was similar to that in embryos blocked at the 2-cell stage (positive control). These results indicate that maternal heat stress enhances oxidative stress in the oviducts and that loss of developmental competence in maternally heat-stressed embryos correlates with a defect in Cdc2 activity at the 2-cell stage.

¹ Supported by a Grant-in-Aid for Exploratory Research (14656098) from the Japan Society for the Promotion of Science to Y.K. and in part by a grant from Morinaga Hoshikai to M.H.

² Correspondence: Yukio Kanai, Institute of Agriculture and Forestry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan. FAX: 81 29 853 6617; kanaiy{at}sakura.cc.tsukuba.ac.jp

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