Multiple action sites of flufenamate on ion transport across the rat distal colon
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Updated: Oct 15, 2026
A Fluorescence-Based Assay of Membrane Potential for High-Throughput Functional Study of Two Endogenous Ion Channels in Two Epithelial Cell Lines
Published on: June 22, 2022
G Schultheiss1, M Frings, G Hollingshaus
1Institut für Veterinär-Physiologie, Justus-Liebig-Universität Giebetaen, Frankfurter Str.100, D-35392 Gieben, Germany.
Abstract:
The antisecretory effects of flufenamate in the rat distal colon were investigated with the Ussing-chamber and the patch-clamp method as well as by measurements of the intracellular Ca(2+) concentration using fura-2-loaded isolated crypts. Flufenamate (5.10(-4) mol l(-1)) suppressed the short-circuit current (Isc) induced by carbachol (5.10(-5) mol l(-1)), forskolin (5.10(-6) mol l(-1)) and the Isc induced by the membrane-permeable analogue of cyclic AMP, CPT - cyclic AMP (10(-4) mol l(-1)). Indomethacin (10(-6) - 10(-4) mol l(-1)) did not mimic the effect of flufenamate, indicating that the antisecretory effect of flufenamate is not related to the inhibition of the cyclo-oxygenase. When the basolateral membrane was depolarized by a high K(+) concentration and a Cl(-) current was induced by a mucosally directed Cl(-) gradient, the forskolin-stimulated Cl(-) current was blocked by flufenamate, indicating an inhibition of the cyclic AMP-stimulated apical Cl(-) conductance. When the apical membrane was permeabilized by the ionophore, nystatin, flufenamate decreased the basolateral K(+) conductance and inhibited the Na(+) - K(+)-ATPase. Patch-clamp experiments revealed a variable effect of flufenamate on membrane currents. In seven out of 11 crypt cells the drug induced an increase of the K(+) current, whereas in the remaining four cells an inhibition was observed. Experiments with fura-2-loaded isolated crypts indicated that flufenamate increased the basal as well as the carbachol-stimulated intracellular Ca(2+) concentration. These results demonstrate that flufenamate possesses multiple action sites in the rat colon: The apical Cl(-) conductance, basolateral K(+) conductances and the Na(+) - K(+)-ATPase.
Insights
Flufenamate exhibits antisecretory effects in rat colon by inhibiting cyclic AMP-stimulated chloride conductance and affecting potassium conductances and Na+-K+-ATPase. Its action is not linked to cyclo-oxygenase inhibition.
Area of Science:
- Gastroenterology
- Pharmacology
- Cell Physiology
Background:
- The distal colon plays a crucial role in regulating fluid and electrolyte balance.
- Understanding the mechanisms of antisecretory agents is vital for treating diarrheal diseases.
Purpose of the Study:
- To investigate the antisecretory effects of flufenamate in the rat distal colon.
- To elucidate the specific molecular targets and mechanisms of flufenamate's action.
Main Methods:
- Ussing-chamber experiments to measure short-circuit current (Isc).
- Patch-clamp technique to assess ion channel activity.
- Intracellular calcium (Ca2+) concentration measurements using fura-2.
- Experiments with ionophores and ion gradients to probe specific conductances.
Main Results:
- Flufenamate suppressed carbachol-, forskolin-, and CPT-cAMP-induced Isc.
- The antisecretory effect was not mediated by cyclo-oxygenase inhibition.
- Flufenamate inhibited cyclic AMP-stimulated apical chloride conductance.
- It decreased basolateral potassium (K+) conductance and inhibited Na+-K+-ATPase.
- Flufenamate increased intracellular Ca2+ concentration.
Conclusions:
- Flufenamate acts on multiple sites in the rat colon.
- Key targets include apical chloride conductance, basolateral K+ conductances, and Na+-K+-ATPase.
- These actions contribute to flufenamate's overall antisecretory properties.
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