Arachidonic acid and prostaglandin E2 activate small-conductance Cl- channels in the basolateral membrane of rabbit parietal cells.

Abstract

1. Cl- channels in the basolateral membrane of non-stimulated parietal cells in isolated rabbit gastric glands were studied by patch-clamp and noise analysis techniques. 2. Voltage-independent whole-cell currents were recorded from parietal cells equilibrated with Cl(-)-containing solutions. Upon reducing the Cl- concentration of the basolateral bathing solution, the current-voltage curve was rapidly shifted to the right. The reversal potential changed according to changes in the equilibrium potential for Cl-. 3. A Cl- channel blocker, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) inhibited whole-cell Cl- currents. The half-maximal inhibitory concentration of NPPB was 300 microM, and the inhibition was reversible (at less than or equal to 200 microM). Another Cl- channel blocker, 4-acetamido-4'-isothiocyanatostilbene-2,2'-dilsulphonic acid or diphenylamine-2-carboxylate was much less effective. 4. The power spectra of whole-cell Cl- current fluctuations contained one Lorentzian component. The single Cl- channel conductance was estimated to be 0.35 pS by the variance noise analysis, which is in agreement with the value obtained by a method of power spectrum analysis (0.29 pS). 5. The addition of arachidonic acid (10 microM) to the basolateral medium markedly increased the whole-cell Cl- current. The combined application of a cyclo-oxygenase inhibitor, indomethacin (50 microM), and a lipoxygenase inhibitor, esculetin (100 microM), increased the Cl- current, whereas the administration of a phospholipase A2 inhibitor, mepacrine (100 microM), significantly decreased the whole-cell Cl- current. 6. A sizeable increase in the whole-cell Cl- current was also induced by a metabolite of arachidonic acid, prostaglandin E2 (10 microM), but not by leukotriene B4 (5 microM) or D4 (10 microM). 7. The present study has shown that small-conductance Cl- channels are present in the basolateral membrane of rabbit parietal cells, and that the channel was functionally regulated by arachidonic acid and prostaglandin E2.