Distribution of potassium in the rat lens.

Rat lenses were incubated for 24 hr in media with various concentrations of potassium and a constant concentration of sodium. The media were prepared by adding potassium chloride to a basic 300 mOsm TC-199 medium. Concentrations of potassium up to 100 mM were produced with a maximum osmolarity of 500 mOsm. The content of lens water remained constant in all media even though the content of potassium doubled and the lens was depolarized. The findings support the view that the content of lens water is determined by the concentration of sodium and that potassium acts like a permeant ion. The loss of potassium in the presence of ouabain during a 24 hr period is about twice as great as it is in a potassium-free medium in the absence of ouabain. This is taken as evidence for the recycling of potassium.