Anion and cation channels in the basolateral membrane of rabbit parietal cells

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Abstract
Ion channels in the basolateral membrane of rabbit parietal cells in isolated gastric glands were studied by the patch clamp technique. Whole-cell current-clamp recordings showed that the membrane potential (E m ) changed systematically as a function of the chloride concentrations of the basolateral bathing solution ([Cl−]0), and of the pipette (intracellular) solution. The relationship betweenE m and [Cl−]0 was not affected by additions of histamine, dibutyryl-cAMP, 4-acetoamido-4′-isothiocyanostilbene-2,2′-disulfonic acid and diphenylamine-2-carboxylate. The whole-cell Cl− conductance was insensitive to voltage. In cell-attached and cell-free patch membranes, however, single Cl− channel opening events could not be observed. The value ofE m depended little on the basolateral K+ concentration, but inward-rectifier K+ currents were observed in the whole-cell configuration, activated by hyperpolarizing pulses and inhibited by extracellular Ba2+. In cell-attached and cell-free patches, openings of single inward-rectifier K+ channels and non-selective cation channels were infrequently recorded. Neither cAMP nor Ca2+ activated these cation channels. The single K+ channel conductance was about 230 pS under the symmetrical high K+ conditions and was inhibited by intracellular tetraethylammonium ions (TEA). The non-selective cation channel had a voltage-independent single conductance of 22 pS and was not inhibited by TEA.