The effect of intracellular cAMP and cystic fibrosis conductance regulator (CFTR) protein on the calcium-activated chloride current (1(CaCl)) present in parotid acinar cells was studied using the patch clamp technique. Application of 1mM of 8-(4-chlorophenylthio)adenosine 3':5'-cyclic monophosphate (CPT-cAMP), a permeable analog of cAMP, inhibited I-CaCl only at positive potentials. This inhibition was partially abolished in cells dialyzed with 20nM PKI 6-22 amide, a potent peptide that specifically inhibits PKA. Because cAMP is an activator of the CFTR Cl- channel, a known regulator of I-CaCl, we also investigated if the inhibition of I-CaCl was mediated by activation of CFTR. To test this idea, we added 1 mM CPT-cAMP to acinar cells isolated from knockout animals that do not express the CFTR channel. In these cells the cAMP effect was totally abolished. Thus, our data provide evidence that cAMP regulates I-CaCl by a dual mechanism involving PKA and CFTR. (C) 2004 Elsevier Inc. All rights reserved.