Whole-cell currents in isolated resting Necturus gastric oxynticopeptic cells.
1. Necturus gastric mucosa secretes Cl- actively across the gastric glands which are composed almost entirely of acid- and enzyme-secreting oxynticopeptic cells. Single channel studies on Necturus oxynticopeptic cells have shown that the basolateral membrane possesses multiple K(+)-selective channels but no observable Cl- channels while the apical membrane has Cl- channels but no observable K+ channels. To relate these channel properties to the conductance of the whole cell we have investigated the macroscopic membrane currents with conventional whole-cell patch-clamp techniques. 2. When bathed in amphibian Ringer solution, gastric oxynticopeptic cells had a membrane resistance of 47.8 +/- 2.8 M omega and a membrane capacitance of 75.5 +/- 2.7 pF (n = 82). This gave a specific membrane resistance of 3260 +/- 160 omega cm2 (n = 82). Reversal potentials of the oxynticopeptic cells were -13.8 +/- 1.2 mV (n = 45) for an intracellular Cl- concentration ([Cl-]i) of 42 mM and were significantly more negative -24.4 +/- 3.1 mV (n = 31, P < 0.001) for [Cl-]i = 22 mM. 3. In the absence of ATP in the pipette solution, there was an 80% reduction of the whole-cell current with a typical half-time (t1/2) of 5 min. The run-down was not observed when the pipette solution contained 4 mM ATP. 4. A slow and voltage-independent inhibition of 80% of the whole-cell currents occurred after addition of NPPB (35 microM). Ba2+ (10 mM) produced a reversible inhibition of 20% of the total current. Together, 35 microM NPPB and 10 mM Ba2+ eliminated 95% of the whole-cell currents. These data suggest that in the resting oxynticopeptic cells Cl- carried the major fraction of the current while K+ ions carried only a small fraction. 5. Total replacement of Cl- in the pipette and bath solution by gluconate- increased the membrane resistance to 751 +/- 104 M omega (n = 53) and shifted the reversal potential to -38.1 +/- 2.8 mV (n = 53). 6. Increasing the bath K+ concentration from 6 to 91 mM activated a current which had a high selectivity for K+ over choline+, Li+, Na+, Rb+ and Cs+ and was independent of Cl-. The activation of this K+ current (IK*) by high external K+ was not seen with ATP-free pipette solution. 7. Ba2+ or Cs+ had a voltage-dependent blocking effect of this inward K+ current. Ouabain (1 mM) or SCH 28080 (200 microM), specific inhibitors of the Na+,K(+)-ATPase and H+,K(+)-ATPase, had no effect.(ABSTRACT TRUNCATED AT 400 WORDS)
Supplisson
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Department of Physiology, UCLA School of Medicine 90024-1751.
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Sachs
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000897:Anti-Ulcer Agents / Q000494:pharmacology; D001464:Barium / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D004594:Electrophysiology; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D009338:Necturus maculosus; D009579:Nitrobenzoates / Q000494:pharmacology; D009994:Osmolar Concentration; D010295:Parietal Cells, Gastric / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D054328:Proton Pump Inhibitors
D000897:Anti-Ulcer Agents; D018118:Chloride Channels; D002712:Chlorides; D007093:Imidazoles; D007473:Ion Channels; D009579:Nitrobenzoates; D015221:Potassium Channels; D054328:Proton Pump Inhibitors; C035235:Sch 28080; D001464:Barium; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D000255:Adenosine Triphosphate; D011188:Potassium