Fig. 8. Schematic diagrams of the four mitochondrion-rich cell types, showing intracellular localization of Na⁺/K⁺-ATPase (red), Na⁺/K⁺/2Cl^- cotransporter (NKCC, cyan) and cystic fibrosis transmembrane conductance regulator (CFTR, green). The movements of ions are focused on Na⁺ and Cl^-, and a K⁺ channel recycling K⁺ is omitted in order to simplify the diagrams. A Cl^- channel (gray) is added on the basolateral membrane of the type-II cell, although its presence was not examined in this study. The presumed interrelationship among the four cell types are indicated by arrows A-E.