| Abstract: | At fertilization, repetitive transient rises of intracellular calcium concentration occur in all mammals studied so far. It has been shown that calcium rises could be induced when mouse fertilized 1-, 2-cell nuclei were trans-planted into unfertilized eggs and that the reconstituted em-bryo could be activated. However, whether the capability of inducing calcium rises occurs in all stages of mammalian embryos remains unknown. In this study, by using the nu-clear transplantation technique and measurement of intra-cellular calcium rises in living cells, we showed that only the nuclei from mouse fertilized 1-cell and 2-cell embryos, nei-ther the nuclei from 4-, 8-cell and ethanol activated parthe-nogenetic embryos nor 2 or 3 nuclei of electrofused 4-cell stage syncytium, have calcium-releasing activity when they were transferred into unfertilized mature oocytes. Our results indicate that the calcium-releasing activity in nuclei of 1-, 2-cell embryos is produced during fertilization and exists at the special stage of fertilized early embryos. These suggested that the capacity of inducing calcium release ac-tivity in fertilized early embryos is important for normal embryonic development. |
