Chloride ion transport in transformed normal and cystic fibrosis epithelial cells

The inability of beta-adrenergic agonists (eg. isoproterenol) to activate a specific apical membrane chloride channel in epithelial cells is characteristic of cystic fibrosis (CF). The study of these channels has been facilitated by the transformation of human airway epithelial cells. Clonal populations of SV40 large T-antigen transformed airway epithelial cells from both normal and cystic fibrosis individuals have been established. A limitation in the use of these cell lines has been the loss of the ability to form tight junctions after multiple subcultures. In particular, this loss appears to be associated with cell "crisis". A selection protocol that involves growing cells in medium that is high in Ca2+ and supplemented with fetal bovine serum (FBS) has been employed to facilitate progression through crisis. One cell line (1HAEo-) that has a normal phenotype and retains tight junctions post-crisis has been produced using this protocol. Immunofluorescent staining with a monoclonal antibody to the E-cadherin adhesion molecule shows a characteristic pericellular localization, indicating the presence of the junctional complex. The presence of tight junctions has been confirmed by electron microscopy. These cells produce elevated (greater than 30 fold) levels of cAMP in response to exposure to isoproterenol or forskolin. Chloride ion transport, as measured by 36Cl- efflux, is stimulated greater than 2 fold by these agents. Three post-crisis CF cell lines which grow in serum-containing medium have been established. These do not exhibit tight junctions. Elevated (greater than 25 fold) levels of cAMP are detected in these cells after addition of isoproterenol or forskolin, but this increase in cAMP is not accompanied by an increase in 36Cl-efflux. Both normal (1HAEo-) and CF cells show increased 36Cl-efflux following addition of the calcium ionophore A23187. (ABSTRACT TRUNCATED AT 250 WORDS)