C ystic fibrosis (CF) is characterized by a defect in cAMP-regulated chloride channels in epithelial cells. The CF gene product CF transmembrane conductance regulator (CFTR) is expressed in the apical membrane of pancreatic duct cells, and mutant CFTR accounts for the pathology in the CF pancreas. PANC 1, a pancreatic duct cell line, has not been considered a good model for studying CFTR and pancreatic chloride transport because CFTR mRNA and protein are undetectable using standard methods. Using electronic cell sizing and cell volume reduction under isotonic conditions, PANC 1 cells were found to possess both cAMP and calcium-activated chloride conductances. Using CFTR antisense oligodeoxynucleotides, the cAMP-activated conductance could be specifically inhibited in a concentration- and time-dependent manner. These findings demonstrate that PANC 1 cells express CFTR and a CFTR-independent calcium-activated chloride channel. With electronic cell sizing and CFTR antisense oligodeoxynucleotides, PANC 1 cells can provide an ideal system for the study of pancreatic duct cell physiology and pathophysiology with respect to the role of CFTR in the pancreas. These findings also suggest that antisense oligodeoxynucleotides may provide a more sensitive yet highly specific means of detecting low levels of expression of CFTR than currently available.