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,I-ATP) were studied in mouse ventricular myocytes. In standard NaCl-containing extracellular solutions, extracellular ATP (100 pm) activated two different currents, I-Cl,I-ATP with a linear I-V relationship in symmetrical Clsolutions, and an inwardly rectifying cation conductance (cationic I-ATP). Cationic I-ATP was selectively inhibited by Gd3+ and Zn2+, or by replacement of extracellular NaCl by NMDG; I-Cl,I-ATP was Cl- selective, and inhibited by replacement of extracellular Cl- by Asp; both currents were prevented by suramin or DIDS pretreatment. In GTPgammaS-loaded cells, I-Cl,I-ATP was irreversibly activated by ATP, but cationic I-ATP was still regulated reversibly. GDPbetaS prevented activation of the I-Cl,I-ATP, even though pertussis toxin pretreatment did not modulate I-Cl,I-ATP. These results suggest that activation of I-Cl,I-ATP occurs via a G-protein coupled P2Y purinergic receptor. The I-Cl,I-ATP persistently activated by GTPgammaS, 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,I-ATP. These results provide compelling evidence that activation of CFTR Cl- channels in mouse heart are coupled to G-protein coupled P2Y purinergic receptors.