The cystic fibrosis (CF), gene product, CF transmembrane conductance regulator (CFTR), is responsible for adenosine 3',5'-cyclic monophosphate (cAMP)-activated Cl- transport in epithelial cells, and mutant CFTR accounts for the pathology in the CF pancreas. We have previously shown that both isolated rabbit pancreatic acini and the human pancreatic duct cell line PANC-1 possess a cAMP-activated Cl- conductance identified as CFTR. We report here that preincubation in either of the female hormones progesterone or beta-estradiol inhibits activation by cAMP, but not by Ca2+ ionophore, of PANC-1 cell volume reduction under isotonic conditions. cAMP-activated cell volume reduction is sensitive to antisense, but not sense, CFTR oligodeoxynucleotide. Furthermore, progesterone inhibits cAMP-activated Cl- efflux from rabbit acinar cells. Moreover preincubation with progesterone, but not beta-estradiol, reduces CFTR mRNA and protein levels as measured using polymerase chain reaction amplification of reverse-transcribed acinar RNA and Western blots of protein from acinar membranes. We conclude that female hormones inhibit CFTR functional activity in pancreatic epithelial cells by different mechanisms.