Influence of exposure to vitrification solutions on 2-cell mouse embryos: II. Osmotic effects or chemical toxicity?

In the companion paper (CryoLetters, 2007, 28:403-408), we reported effects of exposure of two-cell mouse embryos to vitrification solutions containing different vitrificants (EG, PG and DMSO) on the intracellular potassium and sodium content. We also compared exposure of 30% (v:v) ethylene glycol for 1.5 min to the similar experiments with 3-min exposure reported previously (CryoLetters, 2006, 27:87-98). In all experiments, four step protocols (2 steps of addition and 2 steps of washing) were used. Here we present mathematical modeling of the cell osmotic response using the relativistic permeability (RP) approach, which allows calculation of the osmotic curves without using simulation software but by direct calculations of the cell volume, intracellular concentration, and amount of the permeable vitrificants (Cryobiology, 2006, 53:402-3). Magnitude of the maximum cell volume excursion and other important osmotic characteristics were calculated for each step of the protocol, and the results of the mathematical modeling were superimposed onto the experimental data reported and discussed in the companion paper. The osmotic damage vs. specific chemical toxicity of the vitrificants as the major cause of the elemental disturbance of intracellular potassium and sodium content are discussed.