Cigarette smoke extract (CSE) decreases the expression of CFTR but not Na+/K+-ATPase in human bronchial epithelial cells. 16HBE14o- cells were treated with 10% CSE for up to 48 hours (A) or increasing concentrations of CSE prepared from commercial grade cigarettes (Camel) for 48 hours (B). CFTR and Na+/K+-ATPase were detected by immunoblotting. The same amount of protein was loaded in each lane as indicated by detection of β-actin. The blots are representative of at least three independent experiments. (C) Detection of CFTR mRNA transcript levels using quantitative RT-PCR analysis after treatment of 16HBE14o- cells with 10% CSE for 24 hours. Results are expressed as fold change and are representative of three independent experiments. *p < 0.05.