Purpose. To study the expression of P‐glycoprotein (P‐gp), lung resistance‐related protein (LRP), and caveolin‐1 (cav‐1) in the human bronchial epithelial cell line
16HBE14o‐.
Methods. The presence of P‐gp, LRP, and cav‐1 in 16HBE14o‐ cell layers was evaluated using immunocytochemical staining and visuali‐ zation with confocal laser scanning microscopy (CLSM). Functionality of P‐gp was determined by bidirectional transport of rhodamine‐123 with and without a P‐gp inhibitor, verapamil. Caveolae were visualized using transmission electron microscopy (TEM). Flux of fluorescein‐Na was also studied as a paracellular transport marker.
Results. Immunocytochemical staining showed expression of P‐gp localized at the apical membrane of 16HBE14o‐ cell layers. The flux of rhodamine 123 across cell layers exhibited a greater Papp value for the secretory (i.e., basolateral‐to‐apical) direction. This asymmetry disappeared in the presence of verapamil. CLSM provided evidence for the expression of LRP and cav‐1. TEM further showed typically shaped caveolae at the apical and basolateral membranes.
Conclusion. Cell layers of 16HBE14o‐ express drug transport systems that are also present in the human bronchus in vivo, indicating that the 16HBE14o‐ cell line may be a suitable candidate for an in vitro model for mechanistic studies of drug transport processes involved in the smaller airways.
