ATP-INHIBITABLE CL- CHANNEL IN APICAL MEMBRANES OF CULTURED RABBIT CORTICAL COLLECTING DUCT CELLS

Excised patches of apical membranes from immunodissected rabbit cortical collecting duct cells in primary culture were studied by the patch-clamp technique. Barium (1 mM) and tetraethylammonium chloride (5 mM) were added to all solutions to block potassium channel activity. A unique channel was observed that exhibited inward rectification under symmetrical ionic conditions with a measured chord conductance of 54.0 +/- 2.5 pS at - 80 mV (n = 11) and 22.1 +/- 1.7 pS at +80 mV (n = 5). This channel was chloride selective, with a P(Na):P(Cl) of 0.16 (n = 3). Kinetic analysis revealed a voltage-independent open-time probability of 0.80 +/- 0.07 (n = 6). Open-time probability within bursts was 0.96 +/- 0.01. Addition of ATP to the cytosolic surface of the channel resulted in a dose-dependent decrease in open probability, with a threshold effect at 10(-4) M. due to a reduction in burst open time. The effect of ATP was immediate, rapidly reversible at room temperature, and mimicked by GTP, adenosine 5'-O-(3-thiotriphosphate), and guanosine 5-O-(3-thiotriphosphate). This channel may link epithelial chloride permeability to cellular ATP content in the rabbit cortical collecting duct.