Characterization of chloride transport pathways in cultured human keratinocytes.
In human keratinocytes, mediated transport of Cl- was found to occur mainly by two mechanisms: an anion exchange and an electrically conductive pathway. The contribution of the anion exchange, which accounted for about 50% of overall Cl- efflux, was assessed either by its sensitivity to inhibition by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), and by means of Cl- substitution experiments. The anion exchange exhibited a saturation behaviour over the range 10-135 mM Cl-; Cl- was more efficient than HCO3-, Br- and NO3- in increasing Cl- efflux rate, whereas SO4(2-) and I- inhibited Cl- efflux. The electrically conductive Cl- pathway, which accounted for about 40% of total Cl- efflux, was inhibited by the Cl- channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and was at least partially sensitive to variation of the plasma membrane potential. The Cl- channel was insensitive to elevation in the intracellular concentration of either cyclic AMP and calcium ions. Indomethacin, an inhibitor of the cyclooxygenase, failed to reduce Cl- efflux, whereas nordihydroguaiaretic acid (NDGA), an inhibitor of the lipoxygenase, induced 50% inhibition of Cl- efflux. These results support the conclusion that endogenous production of lipoxygenase-derived arachidonic acid metabolite(s) might be responsible for high basal Cl- permeability in human keratinocytes.
Mastrocola
T
T
Dipartimento di Biologia Ev. Sp., Universitá di Bologna, Italy.
De Luca
M
M
Rugolo
M
M
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000838:Anions / Q000378:metabolism; D016718:Arachidonic Acid / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D005942:Gluconates / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism*; D008084:Lipoxygenase / Q000378:metabolism; D009637:Masoprocol / Q000494:pharmacology; D008564:Membrane Potentials
D000838:Anions; D002712:Chlorides; D005942:Gluconates; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D016718:Arachidonic Acid; D009637:Masoprocol; D008084:Lipoxygenase; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid