title: Characterization of apical membrane Cl-dependent Na/H exchange in crypt cells of rat distal colon.
abstract: A novel Cl-dependent Na/H exchange (Cl-NHE) has been identified in apical membranes of crypt cells of rat distal colon. The presence of Cl is required for both outward proton gradient-driven Na uptake in apical membrane vesicles (AMV) and Na-dependent intracellular pH recovery from an acid load in the crypt gland. The present study establishes that Cl-dependent outward proton gradient-driven (22)Na uptake 1) is saturated with increasing extravesicular Na concentration with a Michaelis constant (K(m)) for Na of approximately 24.2 mM; 2) is saturated with increasing outward H concentration gradient with a hyperbolic curve and a K(m) for H of approximately 1.5 microM; 3) is inhibited by the Na/H exchange (NHE) inhibitors amiloride, ethylisopropylamiloride, and HOE-694 with an inhibitory constant (K(i)) of approximately 480.2, 1.1, and 9.5 microM, respectively; 4) is inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, an anion exchange inhibitor at low concentration and a Cl channel blocker at high dose, and by 5-nitro-2(3-phenylpropylamino)benzoic acid, a Cl channel blocker, with a K(i) of approximately 280.6 and 18.3 microM, respectively; and 5) substantially stimulated Cl-NHE activity by dietary Na depletion, which increases plasma aldosterone and inhibits NHE in surface cell AMV. These properties of Cl-NHE are distinct from those of NHE1, NHE2, and NHE3 isoforms that are present in colonic epithelial cells; thus these results suggest that the colonic crypt cell Cl-NHE is a novel NHE isoform.
authors.affiliation: Department of Internal Medicine, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: V M
authors.initials: VM
authors.lastname: Rajendran
authors.forename: J
authors.initials: J
authors.lastname: Geibel
authors.forename: H J
authors.initials: HJ
authors.lastname: Binder
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism* / Q000494:pharmacology; D003106:Colon / Q000166:cytology / Q000378:metabolism*; D004039:Diet, Sodium-Restricted; D004305:Dose-Response Relationship, Drug; D006146:Guanidines / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D009579:Nitrobenzoates / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013450:Sulfones / Q000494:pharmacology
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D006146:Guanidines; D009579:Nitrobenzoates; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D000584:Amiloride; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C039614:ethylisopropylamiloride