Differential Osmotic Behavior of Mammalian Oocytes before and after Maturation: A Quantitative Analysis Using Goat Oocytes as a Model

This study shows that immature and mature goat oocytes respond differently to hyperosmotic stress; when exposed to a 1.5 M propanediol solution, immature oocytes manifest a higher osmotic stress than do mature oocytes. This is the consequence of both higher water permeability (133.9 ± 15.2 vs 82.4 ± 4.4 × 10 -3 cm/min) and lower propanediol permeability (0.87 ± 0.03 vs 1.20 ± 0.03 × 10 -3 cm/min at 20°C) in the immature than in the mature stage. The difference of osmotic behavior between these two types of oocytes is abolished following exposure to cytochalasin D, a drug known to modify the cellular microfilament network. This result suggests differences in actin organization between the two types of oocyte, probably at the cortical level. Calculated values of the intracellular concentration of propanediol as a function of time of exposure show that propanediol rapidly permeates both types of oocyte and that the kinetics of intracellular concentration are lowered by cytochalasin treatment.