Figure 7.

Schematic summary of the distribution of ion channels in rat tracheal epithelial cells. Our immunohistochemical results show that apical anion secretion and cation absorption do not occur in the same cells. Anions, water and mucins (symbolized by secretory vesicles) are secreted to the luminal ASL by secretory goblet cells (center). Ciliated cells (right) promote mucociliary clearance using motile cilia, and also mediate Na⁺ absorption through ENaC proteins. A third cell type, probably representing club cells (left), mediates Ca²⁺‐dependent Cl⁻ secretion through ANO1 channels.