TEMPORAL EFFECTS OF OUABAIN ON IN-VITRO DEVELOPMENT OF MOUSE ZYGOTES

Ouabain is a specific inhibitor of Na+-K+-ATPase, an enzyme which controls the intracellular Na+ and K+ levels. In this study, in-vitro fertilized zygotes from a hybrid mouse strain were used to examine the temporal effects of 50 muM ouabain on embryonic development in vitro during the preimplantation period. A higher incidence of blastocyst formation at the end of the culture period was found when embryos were cultured in the presence of ouabain from 22 to 46 h post-insemination, or any other period that included this time period. When zygotes from randomly bred mice were used, inhibition of Na+-K+-ATPase with ouabain clearly promoted development through the 2-cell block in vitro. As Na+-K+-ATPase is the most important regulator of intracellular electrolyte concentrations in mammalian cells, these results suggest that an ionic imbalance exists in embryos cultured in conventional media which can be positively influenced by inhibiting this enzyme.