Intracellular sodium and potassium concentrations in oocytes of Bufo bufo at the beginning of maturation.

1. During the first phase of maturation in oocytes of Bufo bufo, after the growth phase but before ovulation, intracellular Na rises to 120 m-mole/l. cell water while K falls to 15 m-mole/l. cell water.2. At the same time, the ouabain-insensitive Na efflux and total Na influx both increase while the ouabain-sensitive Na efflux is unchanged.