Variation of water permeability (Lp) and its activation energy (Ea) among unfertilized golden hamster and ICR murine oocytes.

Oocytes provide an excellent model cell type for the exploration of the hypothesis that there is a genetic influence to inter-animal variability in plasma membrane water permeability (Lp) and its activation energy (Ea). Although variability among oocytes pooled across animals has been previously published, variability of oocyte Lp and its Ea among individual animals has yet to be determined. Using a microdiffusion chamber, individual oocytes from five Golden hamsters and six ICR mice were exposed to a 900-mOsm NaCl solution at 37, 22, or 3 degrees C. The resulting change in cell volume over time (dv/dt) was analyzed and hydraulic conductivity (Lp) estimated. The Arrhenius plots (lnLp vs (1/K) x 1000) of the oocytes from each animal were determined and the Ea's were found not to be different among individual Golden hamsters (P > 0.05) with a mean of 7.96 +/- 0.96 Kcal/mol (mean +/- SD). However, the Ea's of the oocytes among individual ICR mice were shown to be significantly different (P < 0.05), with a mean of 11.38 +/- 2.2 Kcal/mol (mean +/- SD). Furthermore, an analysis of the within-mouse and among-mouse variability of Lp was undertaken. The results demonstrated that there was significant variability among ICR mouse oocyte Lp values at all temperatures; however, there was no significant variability within animals. In summary, these data support the hypothesis that significant variability exists in the Lp of ova among mice of the outbred ICR strain. In contrast, the data from the inbred Golden hamster oocyte donors do not show significant variability.