Fig. 1.

Na⁺ and K⁺ transport model in mitochondria-rich epithelial cells of the endolymphatic sac. Large positive electrochemical gradients for Na⁺ promote Na⁺ inflow into the cell from apical and basolateral membrane. Inflowing Na⁺ is actively transported by Na⁺, K⁺-ATPase with a high activity. Na⁺ absorption is followed by water movement from endolymph to the outside