TEMPERATURE-DEPENDENCE OF MATURE MOUSE OOCYTE MEMBRANE PERMEABILITIESIN THE PRESENCE OF CRYOPROTECTANT

Knowledge of cell membrane permeability characteristics facilitates th e design of cryopreservation protocols which minimize damage from osmo tic stress and reduce the incidence of intracellular freezing. Such pe rmeability characteristics can be determined for oocytes from volume m easurements taken during exposure to cryoprotectant. Individual mouse oocytes were held using negative pressure applied to the zona pellucid a by means of a micropipet. Each oocyte was perfused with 1 ml 1.5 mol liter(-1) dimethyl sulfoxide (Me2SO) or propane-1,2-diol at 30, 23, o r 10 degrees C. The osmotic response of each oocyte before, during, an d after perfusion was recorded by videomicroscopy until equilibrium wa s reached. Mean cell diameter across three axes was used to calculate oocyte volume, assuming sphericity, and, using mathematical modeling, values for hydraulic conductivity (L-p) were found to be 0.64, 0.41, a nd 0.20 mu m min(-1) atm(-1) in che presence of Me2SO and 0.53, 0.36 a nd 0.15 in the presence of propane-1,2-diol at 30, 23, and 10 degrees C, respectively. Cryoprotectant permeability (w) was 0.37, 0.16, and 0 .035 for Me2SO and 0.43, 0.24, and 0.04 for propane-1,2-diol, while th e reflection coefficient was 0.98, 0.94, and 0.99 (Me2SO) and 0.76, 0. 99, and 0.95 (propane-1,2-diol) all at 30, 23, and 10, respectively. T he corresponding activation energies (E-a) were 11.65 and 12.23 kCal m ol(-1) for L-p and 23.52 and 22.48 kCal mol(-1) for w, in the presence of Me2SO and propane-1,2-diol, respectively. Values generated for L-p and associated E-a were similar to those found for mouse oocytes in t he absence of cryoprotectant, while w and its E-a were similar to thos e found for oocytes of other species. (C) 1997 Academic Press.