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 differe ntly to hyperosmotic stress; when exposed to a 1.5 M propanediol solut ion, immature oocytes manifest a higher osmotic stress than do mature oocytes. This is the consequence of both higher water permeability (13 3.9 +/- 15.2 vs 82.4 +/- 4.4 x 10(-3) cm/min) and lower propanediol pe rmeability (0.87 +/- 0.03 vs 1.20 +/- 0.03 x 10(-3) cm/min at 20 degre es C) in the immature than in the mature stage. The difference of osmo tic behavior between these two types of oocytes is abolished following exposure to cytochalasin D, a drug known to modify the cellular micro filament network. This result suggests differences in actin organizati on between the two types of oocyte, probably at the cortical level. Ca lculated 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 concentrat ion are lowered by cytochalasin treatment. (C) 1994 Academic Press, In c.