title: Ionic mechanisms of Ca(2+)-dependent electrolyte transport across equine sweat gland epithelium.
abstract: 1. The ionic mechanism involved in Ca(2+)-stimulated electrolyte transport in cultured equine sweat gland epithelial cells was studied using the short-circuit current (ISC) technique. 2. Microscopy revealed that the cultured cells grown on Millipore filters formed polarized monolayers with tight junctions. Monolayers exhibited a mean transepithelial resistance of 333.9 +/- 40.4 omega cm2. 3. Ca(2+)-mobilizing agents, A23187 (1 microM) or thapsigargin (0.01-1 microM), stimulated ISC while forskolin exerted little effect on the ISC. 4. Replacement of external Cl- by gluconate significantly reduced the ISC by 63% when stimulated by 0.1 microM thapsigargin. Residual ISC could be abolished (> 99%) by elimination of HCO3- from the bathing solution. 5. Basolateral addition of bumetanide (0.1 mM), ouabain (0.01 mM) and acetazolamide (45 microM) and apical addition of methyl isobutyl amiloride (MIA, 1-100 microM) all had inhibitory effects on the thapsigargin-stimulated ISC to various extents. 6. Substantial current inhibition could be obtained using 4, 4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) and diphenylamine-2-carboxylate (DPC) in a concentration-dependent manner. 7. The K+ channel blocker barium (5 mM) was effective on both sides of the epithelium with a much larger effect on the basolateral side. 8. The inhibitory effects of acetazolamide, amiloride, MIA, DIDS and DPC on the thapsigargin-stimulated ISC were also observed when a Cl(-)-free solution was used. 9. The results provide evidence for Ca(2+)-stimulated HCO3- as well as Cl- secretion by equine sweat gland epithelium.
authors.affiliation: Department of Physiology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: W H
authors.initials: WH
authors.lastname: Ko
authors.forename: H C
authors.initials: HC
authors.lastname: Chan
authors.forename: S B
authors.initials: SB
authors.lastname: Chew
authors.forename: P Y
authors.initials: PY
authors.lastname: Wong
mesh_terms: D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D001693:Biological Transport, Active / Q000502:physiology; D002118:Calcium / Q000502:physiology*; D002460:Cell Line; D002712:Chlorides / Q000502:physiology; D004573:Electrolytes / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism / Q000648:ultrastructure; D006736:Horses; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008854:Microscopy, Electron; D010539:Permeability; D013545:Sweat Glands / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D001639:Bicarbonates; D002712:Chlorides; D004573:Electrolytes; D004791:Enzyme Inhibitors; D007473:Ion Channels; D019284:Thapsigargin; D002118:Calcium