The early embryo membrane is highly permeable for water, that makes the cell very sensitive to osmotic shock. The cell volume alteration plays an important role in regulation of key cellular functions, including metabolism, protein synthesis and cell death. In the given research, the volume changing of embryonic compartments were determined for isotonic and anisotonic conditions using three- dimensional reconstruction (3-DR). The keeping of the intact volume of the 2-cell mouse embryo was based on freeze-drying technique (Pogorelov & Pogorelova 2008). A Z-stack of optical slices was obtained with laser scanning microscope (LSM) (Zeiss 510, Germany). Osmotic shock was modeled by changes of NaCl contents in Dulbecco's medium. As control we considered the embryo cryofixed immediately after flushing from oviduct. Its volume was calculated as (565) × 10³mm³ (mean the standard deviation). Our data indicates that hypo-osmotic (70 mM NaCl) incubation for 10 minutes resulted in the swelling peak of blastomere volume to (8611) × 10³mm³. After 60 minute incubation the cell volume was recovered to control level. A hyperosmotic (280 mM NaCl) shock induced quick shrinkage of embryonic cells to (312) × 10³mm³ and this effect was irreversible. Note, that incubation in conventional Dulbecco's medium caused a gradual decrease of the blastomere volume to (425) × 10³mm³. The developed technology of LSM tomography of mouse early embryo allows us to measure the cell volume corresponding to the life-like state. Our quantitative data correspond to the qualitative effects observed in vitro.

References: 

Pogorelov, A. & Pogorelova, V. 2008. J.Microsc. 232.