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Whole‐cell currents in isolated resting Necturus gastric oxynticopeptic cells.
Author(s) -
Supplisson S,
Loo D D,
Sachs G
Publication year - 1993
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1993.sp019584
Subject(s) - necturus , reversal potential , pipette , membrane potential , biophysics , chemistry , patch clamp , membrane , intracellular , conductance , voltage clamp , apical membrane , hyperpolarization (physics) , cell membrane , biochemistry , biology , stereochemistry , receptor , nuclear magnetic resonance spectroscopy , mathematics , combinatorics
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)