Changes in intracellular potassium and sodium content of 2-cell mouse embryos induced by exposition to vitrification concentrations of ethylene glycol.

Intracellular concentration of potassium and sodium in two-cell mouse embryos in G1/S phase after exposition to vitrification solutions containing ethylene glycol (EG) and sucrose or after incubation in Dulbecco solution were measured by electron probe microanalysis (EPMA). The embryos at room temperature were treated in 10 percent EG for 10 min, transferred into mixture of EG and 1.0 M sucrose in ratio of 3:7 (v/v) for 3 min, then to 0.5 M sucrose for 10 min followed by washing the cells with Dulbecco;s solution for 10 min prior to analysis. The cytoplasmic concentration of potassium and sodium in controlled untreated with EG embryos were in a range of 116-130 mM of potassium and 120 mM of sodium, with good concordance in two identical experiments. After exposition that mimicked vitrification protocols, the intracellular potassium dropped almost two-three-fold (47 + 3 mM in one experiment and to 70 mM in the second experiment. The intracellular sodium concentration also decreased two-fold in range 60-70 mM after treatment with EG. Possible mechanisms of changes in the intracellular elemental concentrations including the high intracellular sodium observed in intact embryos are discussed.