Extracellular ATP Stimulates Na<SUP>&#8290;</SUP> and Cl<SUP>&#8291;</SUP> Transport through the Activation of Multiple Purinergic Receptors on the Apical and Basolateral Membranes in M-1 Mouse Cortical Collecting Duct Cells

Extracellular ATP Stimulates Na<SUP>&#8290;</SUP> and Cl<SUP>&#8291;</SUP> Transport through the Activation of Multiple Purinergic Receptors on the Apical and Basolateral Membranes in M-1 Mouse Cortical Collecting Duct Cells

<P> The mammalian cortical collecting duct (CCD) plays a major role in regulating renal NaCl reabsorption, which is important in Na<SUP>&#8290;</SUP> and Cl<SUP>&#8291;</SUP> homeostasis. The M-1 cell line, derived from the mouse cortical collecting duct, has been used as a mammalian model of the study on the electrolytes transport in CCD. M-1 cells were grown on collagen-coated permeable support and short circuit current (I<SUB>sc</SUB>) was measured. M-1 cells developed amiloride-sensitive current 5∼7 days after seeding. Apical and basolateral addition of ATP induced increase in I<SUB>sc</SUB> in M-1 cells, which was partly retained in Na<SUP>&#8290;</SUP>-free or Cl<SUP>&#8291;</SUP>-free solution, indicating that ATP increased Na<SUP>&#8290;</SUP> absorption and Cl<SUP>&#8291;</SUP> secretion in M-1 cells. Cl<SUP>&#8291;</SUP> secretion was mediated by the activation of apical cystic fibrosis transmembrane regulator (CFTR) chloride channels and Ca<SUP>2&#8290;</SUP>- activated chloride channels, but Na<SUP>&#8290;</SUP> absorption was not mediated by activation of epithelal sodium channel (ENaC). ATP increased cAMP content in M-1 cells. The RT-PCR analysis demonstrated that M-1 cells express P2Y<SUB>2</SUB>, P2X<SUB>3</SUB> and P2Y<SUB>4</SUB> receptors. These results showed that ATP regulates Na<SUP>&#8290;</SUP> and Cl<SUP>&#8291;</SUP> transports via multiple P2 purinoceptors on the apical and basolateral membranes in M-1 cells.