Regulation of sodium and potassium in muscle fibers of the ventricle of Union, a fresh-water lamellibrach

• 1.

  1. Union ventricle tissue loses potassium and gains sodium in the absence of external potassium. The muscle regions K⁺ and extrudes Na⁺ when returned to potassium-containing medium. Ouabain and 2,4-dinitrophenol, when placed in the pottasium containing medium, inhibit the net movements of both Na⁺ and K⁺.

• 2.

  2. These results suggest that sodium, and possibly potassium, are actively transported. The stoichiometry of potassium and sodium fluxes suggests coupled transport.

• 3.

  3. The rate of unidirectional sodium efflux was reduced by the removal of external potassium, which is consistent with coupled transport of K⁺ and Na⁺.