cAMP activates an ATP-permeable pathway in neonatal rat cardiac myocytes

The molecular mechanisms associated with intracellular ATP release by the h eart are largely unknown. In this study the luciferin-luciferase assay and patch-clamp techniques were used to characterize the pathways responsible f or ATP release in neonatal rat cardiac myocytes (NRCM). Spontaneous ATP rel ease by NRCM was significantly increased after cAMP stimulation under physi ological conditions. cAMP stimulation also induced an anion-selective elect rodiffusional pathway that elicited linear, diphenylamine-2-carboxylate (DP C)-inhibitable Cl- currents in either symmetrical MgCl2 or NaCl. ATP, adeno sine 5'-O-(3-thiotriphosphate), and the ATP derivatives ADP and AMP, permea ted this pathway; however, GTP did not. The cAMP-induced ATP currents were inhibited by DPC and glibenclamide and by a monoclonal antibody raised agai nst the R domain of the cystic fibrosis transmembrane conductance regulator (CFTR). The channel-like nature of the cAMP-induced ATP-permeable pathway was also determined by assessing protein kinase A-activated single channel Cl- and ATP currents in excised inside-out patches of NRCM. Single channel currents were inhibited by DPC and the anti-CFTR R domain antibody. Thus th e data in this report demonstrate the presence of a cAMP-inducible electrod iffusional ATP transport mechanism in NRCM. Based on the pharmacology, patc h-clamping data, and luminometry studies, the data are most consistent with the role of a functional CFTR as the anion channel implicated in cAMP-acti vated ATP transport in NRCM.