Fertilization and early embryology: Temporal effects of ouabain on in-vitro development of mouse zygotes

Ouabain is a specific inhibitor of Na⁺-K⁺-ATPase, an enzymewhich controls the intracellular Na⁺ and K⁺ levels. In thisstudy, in-vitro fertilized zygotes from a hybrid mouse strainwere used to examine the temporal effects of 50 µM ouabainon embryonic development in vitro during the preimplantationperiod. A higher incidence of blastocyst formation at the endof the culture period was found when embryos were cultured inthe presence of ouabain from 22 to 46 h post-insemination, orany other period that included this time period. When zygotesfrom randomly bred mice were used, inhibition of Na⁺-K⁺-ATPasewith ouabain clearly promoted development through the 2-cellblock in vitro. As Na⁺-K⁺-ATPase is the most important regulatorof intracellular electrolyte concentrations in mammalian cells,these results suggest that an ionic imbalance exists in embryoscultured in conventional media which can be positively influencedby inhibiting this enzyme.