Gallbladders from cystic fibrosis (CF) mice (Cftrtm1Cam and Cftrtm2Cam) were examined with the short-circuit current technique. The tissues failed to show any electrogenic anion transport in response to forskolin (cAMP stimulus) but responded to the Ca2+ ionophore ionomycin. Administration of the plasmid pTrial10-CFTR2 complexed with cationic liposomes (3beta-[N-(dimethylaminoethane)-carbamoyl]cholesterol and L-alpha-phosphatidylethanolamine dioleolyl) to the airways restored the phenotype of CF gallbladders to that of the wild type, but did not do so when given orally. Formation of human CFTR mRNA in gallbladders of transfected CF null mice was demonstrated. Using the reporter genes pCMV-luc and pCMV-LacZ, we showed that 1) the intratracheal route was more effective than the oral,intravenous, intramuscular, subcutaneous, or intraperitoneal routes in expressing luciferase activity in the gallbladder and 2) beta-galactosidase staining after pCMV-LacZ was confined to the columnar epithelium lining the gallbladder without any discernible activity in it smooth muscle. The discovery of an unusual route for gene transfer to the biliary system may give useful insight into counteracting the consequences of biliary fibrosis in human CF patients.