Histamine-induced chloride channels in apical membrane of isolated rabbit parietal cells
G Saccomani1, C G Psarras, P R Smith
1Department of Physiology and Biophysics, University of Alabama, Birmingham 35294.
Insights
Histamine stimulation activates chloride channels in rabbit parietal cells, crucial for acid secretion. These channels are voltage-dependent and permeable to various anions, but not significantly to sodium or potassium.
Area of Science:
- Cell Biology
- Physiology
- Membrane Biophysics
Background:
- Parietal cells are key to gastric acid secretion.
- Understanding ion channel function is vital for physiological processes.
Purpose of the Study:
- To investigate the electrical properties of rabbit parietal cell apical membranes.
- To identify and characterize chloride channels involved in acid secretion.
Main Methods:
- Patch-clamp technique on isolated rabbit parietal cells.
- Cell culture and lectin-binding for cell identification.
- Analysis of channel conductance, voltage-dependence, and ion permeability.
Main Results:
- Histamine stimulation (acid secretion) activated voltage-dependent outwardly rectifying Cl- channels (24 +/- 1 pS).
- Channels exhibited high permeability to I-, Br-, and Cl-, low to NO3-, and very low to Na+ or K+.
- Cl- channels were insensitive to Ba2+ and stilbene derivatives but blocked by diphenylamine-2-carboxylic acid.
Conclusions:
- H2-receptor agonist stimulation activates apical Cl- channels in rabbit parietal cells.
- These channels play a significant role in regulating acid secretion.
Abstract:
The electrical properties of the apical membrane of isolated rabbit parietal cells were studied using the patch-clamp technique. The apical membrane of the parietal cells plated on Matrigel and maintained in culture conditions was identified by lectin-binding studies. Cell-attached and excised inside-out patches from 10(-4) M cimetidine-treated parietal cells infrequently contained Cl- channels (9% of the patches). A single class of voltage-dependent outwardly rectifying Cl- channels with 24 +/- 1-pS conductance was observed in 75% of the patches from cells stimulated (acid secreting) by 10(-4) M histamine. Other anions passed through these channels with a permeability sequence of I- (1.2) greater than Br- (1.1) greater than or equal to Cl- (1.0) greater than NO3- (0.7) greater than SO4(2-) (0.1), but there was a very low permeability for Na+ or K+ (PCl-/PNa+ or PCl-/PK+ greater than 5). In inside-out patch configurations the Cl- channel was insensitive to Ba2+ and stilbene derivatives but was inhibited by diphenylamine-2-carboxylic acid in a manner characteristic of a reversible open-channel blocker. It is concluded that H2-receptor agonist stimulation of acid secretion by rabbit parietal cells activates Cl- channels in the apical cell membrane.
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