EDTA stimulates cleavage stage bovine embryo development in culture but inhibits blastocyst development and differentiation

Culture of bovine zygotes in medium SOFaa supplemented with 100 mu M EDTA s ignificantly increased cleavage rates during the first 72 hr of development compared to development in SOFaa. However, continued culture in the presen ce of EDTA for a further 72 hr (total of 6 days of culture) resulted in sig nificantly reduced development to the morulae/blastocyst and blastocyst sta ges compared to culture without EDTA. Highest rates of development to the m orulae/blastocyst stage (56.5%) and to the blastocyst stage (43.2%) were ac hieved when zygotes were cultured for 72 hr with EDTA before transfer to me dium SOFaa without EDTA. Resultant blastocysts also had significantly incre ased blastocyst cell number and ICM cell number compared to those cultured without EDTA in the first 72 hr. EDTA was shown to inhibit glycolytic activ ity of the cleavage stage embryo, thereby preventing the premature stimulat ion of glycolysis and enhancing development. However, EDTA should not be us ed for the later stage embryo as the inhibition of glycolysis reduces energ y production at the blastocyst stage and significantly inhibits inner cell mass development. Mol. Reprod. Dev. 57:256-261, 2000. (C) 2000 Wiley-Liss, Inc.