THE ROLE OF CALCIUM IN DNA-SYNTHESIS AND DEVELOPMENT OF MOUSE PREIMPLANTATION EMBRYOS INVITRO

The effect of calcium upon embryonic growth was studied using cultured mouse preimplantation embryos. Both morphological development of the embryos and embryo DNA synthesis were shown to be dependent on the Ca2 + concentration in the medium in which the embryos were grown. Reducti on of the calcium concentration below 10(-5) M completely blocked cell division and blastocyst formation in the cultured embryos, but only m oderately inhibited embryo DNA synthesis. Trifluoperazine, a calmoduli n antagonist, Strongly inhibited the Ca2+-dependent DNA synthesis in t he embryos. On the other hand, the drug only slightly affected the mor phological development of the embryos. These results demonstrate that calcium independently affects two different aspects of the embryo deve lopment, i.e. DNA synthesis and cell division. It is suggested that th e former effect is calmodulin-dependent, while the latter involves the calcium-dependence of metabolite transport through the cell membranes .