Intracellular distribution of free potassium in Chironomus salivary glands.

Potassium activities have been measured in the nucleus and cytoplasm of Chironomus salivary gland cells, using potassium-selective electrodes. The data provide the first rigorous evidence that potassium is at electrochemical equilibrium across the nuclear membrane. In addition, no difference in potassium chemical activity was found between nucleus and cytoplasm.