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

Abstract

SUMMARY1. C1-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,aM, and the inhibition was reversible (at < 200 /tM). 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 /iiM) to the basolateral medium markedly increased the whole-cell Cl-current. The combined application of a cyclo-oxygenase inhibitor, indomethacin (50,uM), and a lipoxygenase inhibitor, esculetin (100 /tM), increased the Cl-current, whereas the administration of a phospholipase A2 inhibitor, mepacrine (100 /tM), 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 aM), but not by leukotriene B4

Small‐conductance Cl‐ channels in rabbit parietal cells activated by prostaglandin E2 and inhibited by GTP gamma S.

“…We have recently found a small-conductance Cl-channel (0-3-0A4 pS) in the basolateral membrane of rabbit parietal cells using patch-clamp and noise analysis techniques (Sakai, Okada, Morii & Takeguchi, 1992). An important physiological role of the sub-pS Cl-channel is to dominate the cell membrane potential, whereas K+ channels which are present in the basolateral membrane do not significantly contribute to the membrane potential (Sakai, Okada, Morii & Takeguchi, 1989;.…”

A cyclic GMP‐dependent housekeeping Cl− channel in rabbit gastric parietal cells activated by a vasodilator ecabapide

“…Isolated glands were further treated with 500 tyrosine units ml-' of Actinase E at 23-25°C for 5 min. As a result of the additional digestion, parietal cells protruded from the base of glands and had no leaky connection between the intracellular canaliculi and the lumen (Sakai et al, 1992). Isolated gastric glands were suspended in a medium (hereafter, called the respiratory medium; composition, mm NaCl 132.4, KCl 5.4, Na2HPO4 5, NaH2PO4 1, MgSO4 1.2, CaC12 1, HEPES 10, pH 7.35) supplemented with 2 mg ml-' bovine serum albumin and 2 mg ml-' glucose.…”

“…Whole-cell currents recorded from rabbit parietal cells in the isolated gastric glands were previously established to be due to the current through the basolateral membrane (Sakai et al, 1992;Sakai & Takeguchi, 1993). An EPC-7 patch clamp system (List Electronic, Darmstadt, Germany) was used for whole-cell recordings, and necessary corrections were made as described elsewhere (Hamill et al, 1981;Sakai et al, 1992).…”

“…An EPC-7 patch clamp system (List Electronic, Darmstadt, Germany) was used for whole-cell recordings, and necessary corrections were made as described elsewhere (Hamill et al, 1981;Sakai et al, 1992). The following extracellular bathing and intracellular pipette solutions were used (Sakai et al, 1989).…”

“…We have recently reported a membrane potential-dominating (housekeeping) Cl-channel with sub-picosiemens conductance in the basolateral membrane of rabbit gastric parietal cells (Sakai et al, 1992;1995;Sakai & Takeguchi, 1993;. Prostaglandin E2 (PGE2) activates this Cl-channel via the EP3 receptor-mediated Ca2+/ nitric oxide (NO)/cyclic GMP pathway: that is, activation of the EP3 receptor stimulates Ca2+-dependent NO synthase, inducing the subsequent activation of guanylate cyclase .…”