A MINI CL- CHANNEL SENSITIVE TO EXTERNAL PH IN THE BASOLATERAL MEMBRANE OF GUINEA-PIG PARIETAL-CELLS

1. Voltage-independent whole-cell Cl- currents were recorded from both single, isolated parietal cells and parietal cells within gastric gla nds obtained from the fundus of guinea-pig stomach. 2. The Cl- current s were rapidly suppressed by a Cl- channel blocker, NPPB (5-nitro-2(3- phenylpropylamino)-benzoate) , added to the (basolateral) bathing solu tion in a concentration-dependent manner with a half-maximal inhibitio n concentration of 12 mu M. 3. The selectivity sequence among anions w as I->Br->Cl->F-, corresponding to Eisenman's sequence I. 4. The Cl- c urrents were independent of cytosolic Ca2+, cyclic AMP, cyclic GMP, GT P-gamma-S and cell volume, and were not affected by application of aci d secretagogues, omeprazol,arachidonic acid or prostaglandin E(2). 5. Reduction of pH in the (basolateral) bathing solution immediately inhi bited the Cl- current with a pK (-log of K-D) of 6.3, whereas changes in intracellular pH had no effect. 6. The single-channel conductance w as estimated to be 0.46-0.6 pS by variance noise analysis during inhib ition of whole-cell Cl- currents by NPPB or acidic pH. 7. It is conclu ded that pH-sensitive 'mini' Cl- channels, with a sub-picosiemens unit ary conductance, exist in the basolateral membrane of guinea-pig parie tal cells.