Temperature dependence of Kedem-Katchalsky membrane transport coefficients for mature mouse oocytes in the presence of ethylene glycol

Ethylene glycol (EG) is the emerging cryoprotectant of choice for preservation of mammalian embryos but has not been widely used for oocyte preservation. Techniques for oocyte cryopreservation need to be improved before they can be incorporated into routine clinical practice. Hence the permeability characteristics of oocytes in the presence of EG have been determined in order to facilitate the design of cryopreservation protocols using this cryoprotectant. Individual mouse oocytes were held using negative pressure applied to the zona pellucida by means of a micropipet. Each oocyte was perfused with 1 ml 1.5 mol L-1 EG at 30, 19, or 10 degrees C, a total of 10 oocytes being perfused at each temperature. The osmotic response of each oocyte before, during and after perfusion was recorded on videotape. Measurements of mean cell diameter across three axes were used to calculate oocyte volume, assuming them to be spherical, and, using mathematical modeling, values for hydraulic conductivity (L-p) were found to be 0.91 +/- 0.05, 0.51 +/- 0.02, and 0.18 +/- 0.01 mu m min(-1) atm(-1); cryoprotectant permeability (P-EG) was 0.24 +/- 0.01, 0.09 +/- 0.005, and 0.03 +/- 0.004 mu m s(-1); and reflection coefficient (sigma) was 0.98 +/- 0.005, 0.96 +/- 0.01, and 0.97 +/- 0.01 at 30, 19, and 10 degrees C, respectively. The activation energy (E-a) of L-p was 14.0 kCal mol(-1) and of P-EG was 16.4 kCal mol(-1). (C) 1999 Academic Press.