This study is undertaken to identify the regulatory switch for the activation of superoxide radical generation pathway and repression of superoxide dismutase (SOD) at the time of implantation using estrogen as a control factor and delayed implantation as a model system. The results revealed high SOD activity and negligible oxyradical generation in progesterone-treated animals on day-5 and day-8 (delayed implantation) while an enormous rise in oxyradical generation and an abrupt fall in SOD in animals which received both estrogen and progesterone injections were observed on days 5 and 8 of pregnancy. These results strongly suggest that estrogen regulates superoxide anion radical generation by lowering the SOD activity.Blastocyst implantation in the uterus remains an intriguing field in the area of reproductive biology. The immunologically alien blastocyst graft invades actively into a genetically non-identical tissue, the uterus, thereby yielding points of communication between two important current research domains, those of transplantation immunology and invasity of neoplastic tissue. Thus, a thorough study of implantation remains an area of utmost importance, not only for the understanding of one crucial step of mammalian embryology, but also in a wider contact for elucidation of basic concepts in cell biology.
The emergence of the mammalian blastocysts from their thick glycoprotein investment known as the zona pellucida is an important, but poorly understood, event in embryogenesis. In this paper, we demonstrate that peri-hatching blastocysts generate a considerably high quantum of an active oxyradical species for an extremely short period of time when compared to the pre-hatching (unhatched) and post-hatching (hatched) blastocysts. Hatching could be induced in pre-hatching blastocysts by exposing them to superoxide artificially generated to match the observed peri-implantation stage specific levels of superoxide, without impairing their viability. These observations suggest the operation of a superoxide-dependent hatching initiation in developing mammalian embryos.
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