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 (46mV per decade), but E(m) did not change significantly as a function of the K⁺ concentration. The extracellular addition of prostaglandin E₂ (PGE₂; 10 μM) increased the whole-cell Cl^- current. A bifunctional prostaglandin EP3 agonist/EP1 antagonist, 5(Z)-7[(1S, 2S, 3S, 5R)-3-(trans-β- styren)sulfonamido-6,6-dimethylbicyclo-(3.1.1)hept-2-yl]-5-heptenoic acid (ONO-NT-012; 10 μM), 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 μM. The single Cl^- channel conductance was estimated to be 0.29 picosiemens (pS) by variance noise analysis. Both PGE₂ 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 PGE₂ via the EP3 receptor.