title: Effects of NPPB (5-nitro-2-(3-phenylpropylamino)benzoic acid) on chloride transport in intestinal tissues and the T84 cell line.
abstract: NPPB (5-nitro-2-(3-phenylpropylamino)benzoic acid) has been reported to block Cl- channels in isolated rabbit nephrons with high potency (IC50 = 80 nM). The effects of this compound on Cl(-)-mediated transport processes in intestinal tissues have been studied using agonist-stimulated short-circuit current (T84) in Ussing chamber experiments and 36Cl- fluxes in monolayers of a colonic cell line (T84). NPPB inhibited PGE1-stimulated Isc in rabbit distal colon and ileum at concentrations in the range 20 to 100 microM. However, NPPB at the same concentrations also inhibited glucose-stimulated Isc in rabbit ileum, suggesting that its effects were not restricted to those on Cl- transport. Consistent with this, exposure of rabbit distal colon to 100 microM NPPB was found to reduce endogenous ATP levels by 69%, implying that, at these concentrations, NPPB could impair active transport processes by an effect on cellular energy metabolism. Clear evidence for a direct effect of NPPB on epithelial chloride channels was found in studies on Cl- fluxes in T84 cell monolayers. NPPB inhibited VIP-stimulated Cl- uptake into T84 cells with an IC50 of 414 microM. NPPB (1 mM) also inhibited Cl- efflux from pre-loaded cells confirming its effect as a weak Cl- channel blocker in this system.
authors.affiliation: Gastrointestinal Research, SmithKline Beecham, The Frythe, Welwyn, U.K.
authors.forename: D J
authors.initials: DJ
authors.lastname: Keeling
authors.forename: A G
authors.initials: AG
authors.lastname: Taylor
authors.forename: P L
authors.initials: PL
authors.lastname: Smith
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D002460:Cell Line; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000378:metabolism*; D006801:Humans; D007082:Ileum / Q000378:metabolism*; D007408:Intestinal Absorption / Q000187:drug effects*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism; D009579:Nitrobenzoates / Q000494:pharmacology*; D011817:Rabbits
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D009579:Nitrobenzoates; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid