哺乳動物胚の初期発生における細胞内カルシウムイオンの役割

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The present study was conducted to examine the effects of intracellular calcium on embryo development in mammals.1) Intracellular Ca^<2+> concentrations of oocytes fertilized in vitro were monitored continuously starting from at fertilization to the end of the oscillations. The data showed that intracellular Ca^<2+> oscillations were stopped around the time of pronuclear formation, 3-4 hours after insemination. Sperm derived Ca^<2+> releasing activity was localized into both male and female pronuclei.2) The optimal conditions for inducing parthenogenetic activation by strontium were examined and the development ability of the activated oocytes was accessed in mice. In oocytes derived from B6CBF1 mice more than 90% of oocytes were activated by the treatment with strontium for 30 min, forming the second polar body and a single pronucleus. The ability to develop to blastocysts was improved in diploid parthenogenetic embryos ; 93% were developed to the blastocyst stage and 11% of the embryos developed to day 10 of gestation. These data clearly showed that strontium is a potent stimulus for inducing parthenogenetic activation in mouse oocytes.3) The effect of repetitive electrical pulses to recipient ooplasts and donor blastomeres on the development was examined in the nuclear transferred bovine embryos. A series of repetitive electrical pulses with 30 min intervals improved the rates of activated oocytes and the pronuclear formation in oocytes matured in vitro. After fusion with a donor nucleus, more than 20% of the reconstituted embryos developed blastocyst stage in vitro. Additional electrical pulses before fusion to the donor blastomeres and recipients ooplasts significantly enhanced the percentage of reconstituted embryos developing to the blastocysts (38%). These results suggest that a series of repetitive electrical pulses can induce palatable oocyte activation and enhance the development of nuclear transferred bovine embryos.