Regulation of Na+, K+ ATPase activity during meiotic maturation of Pleurodeles waltl oocytes. Role of calcium.

Changes in activity of the Na+, K+ ATPase of maturing Pleurodeles waltl were followed by measuring the resting potential in presence or absence of the specific inhibitor dihydroouabain. Corresponding currents were measured in voltage clamp conditions to eliminate the differences in resting potential at the origin and at the end of the meiotic maturation process. Our data confirm previous results obtained on Xenopus, indicating that the Na+,K+ pump activity disappears from the plasma membrane during progesterone-induced maturation and can be reactivated by an increase in internal Ca2+ triggered by ionomycin. Moreover we show by ultrastructural histochemistry that these modulations are likely to depend on the internalization and reinsertion of the transporter into the plasma membrane.