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Quantifying Agonist Activity at G Protein-coupled Receptors
Published on: December 26, 2011
Ouabain binding to isolated frog gastric mucosa
The American Journal of Physiology
|August 1, 1981
Summary
Potassium ions (K+) play a crucial role in regulating gastric acid secretion. Increasing external K+ significantly reduces ouabain
Area of Science:
- Physiology
- Cell Biology
- Biochemistry
Background:
- Cardiac glycosides like ouabain inhibit gastric acid secretion.
- Elevating external potassium (K+) reduces this inhibitory effect.
- The precise role of K+ in ouabain's action on gastric acid secretion remains unclear.
Purpose of the Study:
- To investigate the role of potassium (K+) in ouabain-induced inhibition of gastric acid secretion.
- To determine the effect of K+ on [3H]ouabain binding in isolated bullfrog gastric mucosa.
Main Methods:
- Measurement of [3H]ouabain binding in isolated bullfrog gastric mucosa.
- Assay of Na+-K+-ATPase activity in mucosal homogenates.
- Manipulation of K+ and Na+ concentrations in bathing solutions to assess effects on acid secretion and ouabain binding.
Main Results:
- [3H]ouabain uptake exhibited saturable (specific) and linear (non-specific) binding components.
- Specific ouabain binding correlated with Na+-K+-ATPase activity.
- Increased external K+ or replacement of Na+ with K+ reversed ouabain's inhibition of acid secretion without altering maximum specific binding.
Conclusions:
- Na+-K+-ATPase in oxyntic cells is essential for maintaining intracellular K+ levels.
- High intracellular K+ supports apical K+/H+ exchange, crucial for acid secretion.
- This mechanism explains how K+ modulates ouabain's effect on gastric acid secretion.
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