Growth of mouse embryos in bicarbonate media buffered by carbon dioxide, hepes, or phosphate

The purpose of this study was to determine if mouse embryos could be grown successfully in a culture medium devoid of the carbon dioxide phase (CO2). Mouse embryos fertilized in vivo were collected and cultured in Hepes medium with and without bicarbonate (HCO3-) and a phosphate medium with and without HCO3-. In these experiments no CO2 gas phase was used. Further embryos were cultured in Whittingham's modified Tyrode's (T6) medium with a CO2 gas phase and served as controls. The degree of embryonic development was noted. Surviving blastocysts were transferred to the uteri of pseudopregnant mice and delivery at term was allowed to occur. There was no significant difference in the degree of embryonic development in those embryos cultured in T6 or Hepes medium (+ HCO3-) or in the number of live offspring obtained when these blastocysts were placed within the mouse uterus. Although embryonic development apparently proceeded successfully in the phosphate (+ HCO3-) medium, none of these blastocysts survived when transferred to mouse uteri. No embryonic growth occurred in either the Hepes or phosphate media which were devoid of HCO3-. It appears that a Hepes medium containing HCO3-, which uses no CO2 gas phase, is as effective as T6 medium, which uses a gas phase, in supporting in vitro mouse embryonic growth.