Primary cultures of the dog's tracheal epithelium: Fine structure,fluid, and electrolyte transport

Summary Cells from the dog's tracheal mucosa formed confluent epithelial sheets in culture. Typical tight junctions separated the apical from the basolateral portion of the cell membrane. The apical portion of the cell contained numerous short microvilli and a pronounced glycocalyx. The basolateral portion of the plasma membrane was unspecialized except for extensive gap junctions between cells. Freeze-fracture showed that the cultured cells lacked the basolateral square (orthogonal) arrays of the original tissue, particles previously implicated in ion transport. Formation of domes indicated the presence of active fluid absorption. Domes appeared between days 4 and 8 of culture and persisted for about 1 week. Cell sheets showed a transepithelial resistance of 400 ·cm² and a short-circuit current (I_sc) of 5 A·cm^–2. The effects of transport inhibitors indicated that both active Na absorption and active Cl secretion were present. I_sc was increased by isoproterenol, prostaglandins E₂ and F₂, vasoactive intestinal peptide, dibutyryl cyclic AMP, leukotrienes C₄ and D₄, and bradykinin. These changes were probably due to stimulation of active Cl secretion.