Cl-HCO3 and Cl-OH exchanges mediate Cl uptake in apical membrane vesicles of rat distal colon

1993 ◽  
Vol 264 (5) ◽  
pp. G874-G879 ◽  
Author(s):  
V. M. Rajendran ◽  
H. J. Binder
Keyword(s):  
Apical Membrane ◽  
Kinetic Constant ◽  
Membrane Vesicles ◽  
Distal Colon ◽  
Ph Gradient ◽  
Disulfonic Acid ◽  
Ph Homeostasis ◽  
Rat Distal Colon ◽  
Hyperbolic Curve ◽  
Apical Membrane Vesicles

This study describes Cl-HCO3 and Cl-OH exchanges as the mechanism for Cl uptake by apical membrane vesicles (AMV) of rat distal colon. Although HCO3 gradient-stimulated 36Cl uptake was additionally stimulated by the additional presence of a pH gradient, pH gradient-stimulated 36Cl uptake was not further enhanced by a HCO3 gradient. HCO3 gradient-stimulated and OH gradient-stimulated 36Cl uptake was not inhibited by voltage clamping, with K and its ionophore valinomycin, but was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, an anion exchange inhibitor, with an apparent inhibitory constant of 7.8 and 106.0 microM, respectively. Increasing intravesicular OH concentration in the absence of HCO3 (with fixed extravesicular Cl concentration) yielded a sigmoidal curve for 36Cl uptake. In contrast, increasing intravesicular OH concentration in the presence of equimolar intra- and extravesicular HCO3 (25 mM) yielded a saturable hyperbolic curve. Increasing extravesicular Cl concentration saturated both HCO3 gradient-stimulated and OH gradient-stimulated 36Cl uptake, with a kinetic constant for Cl of approximately 11.9 and 22.6 mM, respectively. We conclude that Cl uptake in AMV of rat distal colon occurs via two separate anion (Cl-HCO3 and Cl-OH) exchange processes. We speculate that one of these two anion exchanges may be responsible for transcellular Cl movement, while the other may be important in the regulation of intracellular pH homeostasis.

Distribution and regulation of apical Cl/anion exchanges in surface and crypt cells of rat distal colon

1999 ◽  
Vol 276 (1) ◽  
pp. G132-G137 ◽  
Author(s):  
Vazhaikkurichi M. Rajendran ◽  
Henry J. Binder
Keyword(s):  
Spatial Distribution ◽  
Concentration Gradient ◽  
Apical Membrane ◽  
Membrane Vesicles ◽  
Distal Colon ◽  
Ph Homeostasis ◽  
Rat Distal Colon ◽  
Na Depletion ◽  
Crypt Cells ◽  
Apical Membrane Vesicles

Na depletion inhibits electroneutral Na-Cl absorption in intact tissues and Na/H exchange in apical membrane vesicles (AMV) of rat distal colon. Two anion (Cl/HCO3 and Cl/OH) exchanges have been identified in AMV from surface cells of rat distal colon. To determine whether Cl/HCO3 and/or Cl/OH exchange is responsible for vectorial Cl movement, this study examined the spatial distribution and the effect of Na depletion on anion-dependent 36Cl uptake by AMV in rat distal colon. These studies demonstrate that HCO3 concentration gradient-driven36Cl uptake (i.e., Cl/HCO3 exchange) is 1) primarily present in AMV from surface cells and 2) markedly reduced by Na depletion. In contrast, OH concentration gradient-driven36Cl uptake (i.e., Cl/OH exchange) present in both surface and crypt cells is not affected by Na depletion. In Na-depleted animals HCO3 also stimulates36Cl via Cl/OH exchange with low affinity. These results suggest that Cl/HCO3 exchange is responsible for vectorial Cl absorption, whereas Cl/OH exchange is involved in cell volume and/or cell pH homeostasis.

Isolation and characterization of apical membrane vesicles of the rat distal colon

1995 ◽  
Vol 195 (1) ◽  
pp. 333-342 ◽  
Author(s):  
Oliver Schröder ◽  
Ralf Gerhard ◽  
Wolfgang F. Caspary ◽  
Jürgen Stein
Keyword(s):  
Apical Membrane ◽  
Membrane Vesicles ◽  
Distal Colon ◽  
Isolation And Characterization ◽  
Rat Distal Colon ◽  
Apical Membrane Vesicles

Mercaptopropionate inhibits butyrate uptake in isolated apical membrane vesicles of the rat distal colon

1995 ◽  
Vol 108 (3) ◽  
pp. 673-679 ◽  
Author(s):  
Jürgen Stein ◽  
Oliver Schröder ◽  
Vladan Milovic ◽  
Wolfgang F. Caspary
Keyword(s):  
Apical Membrane ◽  
Membrane Vesicles ◽  
Distal Colon ◽  
Rat Distal Colon ◽  
Apical Membrane Vesicles

Characterization of apical membrane Cl-dependent Na/H exchange in crypt cells of rat distal colon

2001 ◽  
Vol 280 (3) ◽  
pp. G400-G405 ◽  
Author(s):  
Vazhaikkurichi M. Rajendran ◽  
John Geibel ◽  
Henry J. Binder
Keyword(s):  
Channel Blocker ◽  
Apical Membrane ◽  
Distal Colon ◽  
Proton Gradient ◽  
Disulfonic Acid ◽  
High Dose ◽  
Cl Channel ◽  
Rat Distal Colon ◽  
Na Uptake ◽  
Crypt Cells

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 22Na uptake 1) is saturated with increasing extravesicular Na concentration with a Michaelis constant ( K m) for Na of ∼24.2 mM; 2) is saturated with increasing outward H concentration gradient with a hyperbolic curve and a K m for H of ∼1.5 μM; 3) is inhibited by the Na/H exchange (NHE) inhibitors amiloride, ethylisopropylamiloride, and HOE-694 with an inhibitory constant ( K i) of ∼480.2, 1.1, and 9.5 μM, 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 ∼280.6 and 18.3 μM, 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.

Evidence for location of the CFTR in human placental apical membrane vesicles

1995 ◽  
Vol 269 (1) ◽  
pp. C148-C155 ◽  
Author(s):  
D. P. Faller ◽  
D. A. Egan ◽  
M. P. Ryan
Keyword(s):  
Ion Transport ◽  
Apical Membrane ◽  
Potassium Concentration ◽  
Membrane Vesicles ◽  
Protein Band ◽  
Disulfonic Acid ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Cystic Fibrosis Transmembrane ◽  
Apical Membrane Vesicles

Ion transport (36Cl uptake) and immunochemical studies were undertaken to detect the cystic fibrosis transmembrane conductance regulator (CFTR) in apical membrane vesicles prepared from human placenta. 36Cl uptake into membrane vesicles was studied in the absence and presence of inwardly directed potassium gradients and valinomycin (Ko = Ki and Ko > Ki, where Ko is potassium concentration outside and Ki is potassium concentration inside the vesicles). The sensitivities of 36Cl uptake to the inhibitors 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), bumetanide, and diphenylamine-2-carboxylate were investigated. Each compound significantly inhibited uptake under both sets of conditions. Additional inhibition of 36Cl uptake was found when the compounds were added together, indicating that they were acting at least partly on different components of the 36Cl uptake. The DIDS- and bumetanide-insensitive component of transport was more selective for Cl than I. These findings suggested that this component may, at least in part, represent Cl transport via CFTR. Addition of adenosine 5'-O-(3-thiotriphosphate) (0.8 mM) led to a decrease in total 36Cl uptake but masked in the overall decrease was an increase in the DIDS- and bumetanide-insensitive component of 36Cl uptake. Western blot analysis of the apical membrane proteins with an antibody specific for a region of human CFTR detected a protein band of approximately 190 kDa. These ion transport and immunochemical studies provide evidence that CFTR is located in human placental apical membrane vesicles.

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