Temperature-dependent osmotic behavior of germinal vesicle and metaphase II stage bovine oocytes in the presence of Me2SO in relationship to cryobiology

Plasma membrane permeability coefficients and their activation energies (E- a) for water (L-p) and dimethyl sulfoxide (P-Me2SO) as well as the reflecti on coefficient (sigma) were determined for germinal vesicle (GV) and metaph ase II (MII) bovine oocytes. a micropipette perfusion technique was used wi th a temperature controlled circulation chamber, which was adapted to a mic romanipulator. Experiments were performed at five different temperatures (3 0, 20, 10, 4 and -3 degrees C). The Kedem and Katchalsky model was assumed and L-p, P-Me2SO and a were estimated. Estimated permeability values from t he experimental temperatures were then applied to Arrhenius plots In(L-p) o r In(P-Me2SO) vs 1/Temperature (K) to estimate the activation energies (E-a ) for L-p(Me2SO) and P-Me2SO. The estimated E-a for L-p(Me2SO) for GV and M II oocytes were 23.84 Kcal/mol and 8.46 Kcal/mol, respectively. The E-a for P-Me2SO were 21.0 Kcal/mol and 23.20 Kcal/mol, respectively. The correlati on (r(2)) for these linear regression plots for GV oocytes were 0.83 and 0. 95 for L-p(Me2SO) and P-Me2SO, respectively. For MII oocytes, r(2) values w ere 0.95 and 0.99 for L-p(Me2SO) and P-Me2SO, respectively There was a poss ible discontinuity detected in the Arrhenius plot for L-p(Me2SO) for GV ooc ytes. A significant decrease of the reflection coefficient was observed at 10 degrees C compared to other experimental temperatures. These data provid e a fundamental basis that should be taken into account for low temperature preservation of bovine oocytes in the presence of Me2SO. (C) 1999 Wiley-Li ss, Inc.