Direct modulation of tracheal Cl--channel activity by 5,6- and 11,12-EET.
Using microelectrode potential measurements, we tested the involvement of Cl- conductances in the hyperpolarization induced by 5,6- and 11,12-epoxyeicosatrienoic acid (EET) in airway smooth muscle (ASM) cells. 5,6-EET and 11,12-EET (0.75 microM) caused -5.4 +/- 1.1- and -3.34 +/- 0.95-mV hyperpolarizations, respectively, of rabbit tracheal cells (from a resting membrane potential of -53.25 +/- 0.44 mV), with significant residual repolarizations remaining after the Ca2+-activated K+ channels had been blocked by 10 nM iberiotoxin. In bilayer reconstitution experiments, we demonstrated that the EETs directly inhibit a Ca2+-insensitive Cl- channel from bovine ASM; 1 microM 5,6-EET and 1.5 microM 11,12-EET lowered the unitary current amplitude by 40 (n = 6 experiments) and 44.7% (n = 4 experiments), respectively. Concentration-dependent decreases in channel open probability were observed, with estimated IC50 values of 0.26 microM for 5,6- and 1.15 microM for 11,12-EET. Furthermore, pharmacomechanical tension measurements showed that both regioisomers induced significant bronchorelaxations in epithelium-denuded ASM strips. These results suggest that 5,6- and 11,12-EET can act in ASM as epithelium-derived hyperpolarizing factors.
Salvail
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Le Bilarium, Department of Physiology and Biophysics, Faculty of Medicine, University of Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4.
Dumoulin
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Rousseau
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D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002417:Cattle; D002586:Cesium / Q000502:physiology; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000502:physiology*; D002712:Chlorides / Q000502:physiology; D004847:Epithelial Cells / Q000502:physiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008839:Microelectrodes; D008861:Microsomes / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D010455:Peptides / Q000494:pharmacology; D011817:Rabbits; D014132:Trachea / Q000187:drug effects / Q000502:physiology*
D018118:Chloride Channels; D002712:Chlorides; D010455:Peptides; D002586:Cesium; C046783:11,12-epoxy-5,8,14-eicosatrienoic acid; C064719:iberiotoxin; C040776:5,6-epoxy-8,11,14-eicosatrienoic acid; D002217:Carbachol; D015126:8,11,14-Eicosatrienoic Acid; C028019:cesium chloride; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid