P2Y purinergic receptor regulation of CFTR chloride channels in mouse cardiac myocytes

The intracellular signalling pathways and molecular mechanisms responsible for P2‐purinoceptor‐mediated chloride (Cl − ) currents ( I Cl,ATP ) were studied in mouse ventricular myocytes. In standard NaCl‐containing extracellular solutions, extracellular ATP (100 μ m ) activated two different currents, I Cl,ATP with a linear I–V relationship in symmetrical Cl − solutions, and an inwardly rectifying cation conductance (cationic I ATP ). Cationic I ATP was selectively inhibited by Gd 3+ and Zn 2+ , or by replacement of extracellular NaCl by NMDG; I Cl,ATP was Cl − selective, and inhibited by replacement of extracellular Cl − by Asp − ; both currents were prevented by suramin or DIDS pretreatment. In GTPγS‐loaded cells, I Cl,ATP was irreversibly activated by ATP, but cationic I ATP was still regulated reversibly. GDPβS prevented activation of the I Cl,ATP, even though pertussis toxin pretreatment did not modulate I Cl,ATP . These results suggest that activation of I Cl,ATP occurs via a G‐protein coupled P2Y purinergic receptor. The I Cl,ATP persistently activated by GTPγS, was inhibited by glibenclamide but not by DIDS, thus exhibiting known pharmacological properties of cystic fibrosis transmembrane conductance regulator (CFTR) Cl − channels. In ventricular cells of cftr −/− mice, extracellular ATP activated cationic I ATP , but failed to activate any detectable I Cl,ATP . These results provide compelling evidence that activation of CFTR Cl − channels in mouse heart are coupled to G‐protein coupled P2Y purinergic receptors.