Prostaglandin E2-activated housekeeping Cl- channels in the basolateral membrane of rat gastric parietal cells

Cl- channels in the basolateral membrane of parietal cells within isolated rat gastric glands were studied by the whole-cell patch-clamp technique. The membrane potential (E-m) of non-stimulated parietal cells changed as a function of the basolateral extracellular Cl- concentration (46 mV per decade), but E-m did not change significantly as a function of the K+ concentration. The extracellular addition of prostaglandin E-2 (PGE(2); 10 mu M) increased the whole-cell Cl- current. A bifunctional prostaglandin EP3 agonist/EP1 antagonist, 5(Z)-7-[(1S,2S,3S,5R)-3-(trans-beta-styren)sulfonamido-6,6-dimethylbicyclo-(3.1.1)hept-2-yl]-5-heptenoic acid (ONO-NT-012; 10 mu M), also increased the Cl- current. Basal Cl- currents and the PGE(2) and ONO-NT-012-increased Cl- currents were voltage-independent and inhibited by a Cl- channel blocker, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), at 500 mu M. The single Cl- channel conductance was estimated to be 0.29 picosiemens (pS) by variance noise analysis. Both PGE(2) and ONO-NT-012 increased intracellular free Ca2+ concentration in the fura-2-loaded parietal cell transiently. The present study has shown that housekeeping sub-pS Cl- channels are present in the basolateral membrane of rat parietal cell, and that the channels are regulated positively by PGE(2) via the EP3 receptor.