ALLEVIATION OF THE 2-CELL BLOCK AND DEVELOPMENT TO THE BLASTOCYST OF CF1 MOUSE EMBRYOS - ROLE OF AMINO-ACIDS, EDTA AND PHYSICAL PARAMETERS

The role of amino acids, ethylenediaminetetraacetic acid (EDTA), trans ferrin, oxygen, glucose, glutamine, taurine and ammonium in CF1 mouse zygote development in culture was examined, Non-essential amino acids and glutamine were shown to alleviate the 2-cell block in culture, and acted in synergy with EDTA to facilitate development to the blastocys t stage, In the presence of amino acids and EDTA, transferrin conferre d no beneficial effect, Development of zygotes was significantly impai red if amino acids were removed from the collection medium, even when they were subsequently cultured in the presence of amino acids, Zygote development to the blastocyst stage was significantly improved when m odular incubator chambers were used compared to using a conventional i ncubator, and when an oxygen concentration of 7% was used as opposed t o 20%, Addition of taurine to medium containing non-essential amino ac ids had no effect on embryo development, whereas the removal of glutam ine and/or glucose from the culture medium significantly reduced blast ocyst cell number. Removal of glucose from the culture medium also res ulted in a significant decrease in implantations, Ammonium, generated from the breakdown of amino acids, significantly reduced blastocyst de velopment. EDTA was found to confer its beneficial effects during the first 48 h of culture, and indeed was inhibitory during the second 48 h, resulting in loss of subsequent viability, In summary, the data dem onstrate that development of CF1 zygotes to the blastocyst stage is re adily achievable. In the presence of nonessential amino acids and glut amine the removal of glucose is detrimental to CF1 mouse embryo develo pment in culture and reduces subsequent viability, Optimal development and maintenance of viability requires more than one culture medium to support the preimplantation period.