Multiple action sites of flufenamate on ion transport across the rat distal colon.
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.
Schultheiss
G
G
Institut für Veterinär-Physiologie, Justus-Liebig-Universität Giebetaen, Frankfurter Str.100, D-35392 Gieben, Germany.
Frings
M
M
Hollingshaus
G
G
Diener
M
M
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001485:Basement Membrane / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D003106:Colon / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005439:Flufenamic Acid / Q000494:pharmacology*; D005453:Fluorescence; D016257:Fura-2; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D017136:Ion Transport / Q000187:drug effects; D007811:Lanthanum / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar
D000894:Anti-Inflammatory Agents, Non-Steroidal; D002712:Chlorides; D005576:Colforsin; D005439:Flufenamic Acid; D007811:Lanthanum; D002217:Carbachol; D000242:Cyclic AMP; D002118:Calcium; D016257:Fura-2; D007213:Indomethacin