title: Activation of the basolateral membrane Cl- conductance essential for electrogenic K+ secretion suppresses electrogenic Cl- secretion.
abstract: Adrenaline activates transient Cl(-) secretion and sustained K(+) secretion across isolated distal colonic mucosa of guinea-pigs. The Ca(2+)-activated Cl(-) channel inhibitor CaCCinh-A01 (30 μm) significantly reduced electrogenic K(+) secretion, detected as short-circuit current (I(sc)). This inhibition supported the cell model for K(+) secretion in which basolateral membrane Cl(-) channels provide an exit pathway for Cl(-) entering the cell via Na(+)-K(+)-2Cl(-) cotransporters. CaCCinh-A01 inhibited both I(sc) and transepithelial conductance in a concentration-dependent manner (IC(50) = 6.3 μm). Another Cl(-) channel inhibitor, GlyH-101, also reduced sustained adrenaline-activated I(sc) (IC(50) = 9.4 μm). Adrenaline activated whole-cell Cl(-) current in isolated intact colonic crypts, confirmed by ion substitution. This adrenaline-activated whole-cell Cl(-) current was also inhibited by CaCCinh-A01 or GlyH-101. In contrast to K(+) secretion, CaCCinh-A01 augmented the electrogenic Cl(-) secretion activated by adrenaline as well as that activated by prostaglandin E(2). Synergistic Cl(-) secretion activated by cholinergic/prostaglandin E(2) stimulation was insensitive to CaCCinh-A01. Colonic expression of the Ca(2+)-activated Cl(-) channel protein Tmem16A was supported by RT-PCR detection of Tmem16A mRNA, by immunoblot with a Tmem16A antibody, and by detection of immunofluorescence in lateral membranes of epithelial cells. Alternative splices of Tmem16A were detected for exons that are involved in channel activation. Inhibition of K(+) secretion and augmentation of Cl(-) secretion by CaCCinh-A01 support a common colonic cell model for these two ion secretory processes, such that activation of basolateral membrane Cl(-) channels contributes to the production of electrogenic K(+) secretion and limits the rate of Cl(-) secretion. Maximal physiological Cl(-) secretion occurs only for synergistic activation mechanisms that close these basolateral membrane Cl(-) channels.
authors.affiliation: Department of Neuroscience, Cell Biology & Physiology, Wright State University Boonshoft School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA.
authors.forename: Quanhua
authors.initials: Q
authors.lastname: He
authors.forename: Susan T
authors.initials: ST
authors.lastname: Halm
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.forename: Dan R
authors.initials: DR
authors.lastname: Halm
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D002712:Chlorides / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D018678:Cholinergic Agents / Q000494:pharmacology; D003106:Colon / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism; D004837:Epinephrine / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006168:Guinea Pigs; D006834:Hydrazines / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D011188:Potassium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D018678:Cholinergic Agents; D006834:Hydrazines; D008565:Membrane Proteins; C548779:N-(2-naphthalenyl)-((3,5-dibromo-2,4-dihydroxyphenyl)methylene)glycine hydrazide; D028021:Sodium-Potassium-Chloride Symporters; D015232:Dinoprostone; D011188:Potassium; D005998:Glycine; D004837:Epinephrine