(A-C) Electron microscopy, rat. Caveolae were identified in the basal (A and B, arrows) and in the lateral membrane (C, arrowheads) of ciliated cells in the rat trachea. (D-I) Electron-microscopy and immunohistochemistry, wild-type mouse. Caveolae were present only in the basal cells of the mouse trachea (E and F, arrows) and only this cell type was immunoreactive for cav-1α (D, arrowheads). (G-I) In tracheal epithelial cells of cav-1 deficient mice, neither cav-1α-immunoreactivity (G) nor caveolae (H and I) were found in the basal cells.