Factors affecting chloride conductance in apical membrane vesicles from human placenta

1992 ◽  
Vol 130 (3) ◽  
Author(s):  
Don Faller ◽  
MichaelP. Ryan
Keyword(s):  
Human Placenta ◽  
Apical Membrane ◽  
Membrane Vesicles ◽  
Chloride Conductance ◽  
Factors Affecting ◽  
Apical Membrane Vesicles

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.

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.

Na+ transport in human proximal colonic apical membrane vesicles

1994 ◽  
Vol 106 (1) ◽  
pp. 125-133 ◽  
Author(s):  
Edward J. Cragoe ◽  
Pradeep K. Dudeja ◽  
James M. Harig ◽  
Melissa L. Baldwin ◽  
Krishnamurthy Ramaswamy ◽  
...  
Keyword(s):  
Apical Membrane ◽  
Membrane Vesicles ◽  
Na Transport ◽  
Apical Membrane Vesicles
Sign in / Sign up

Export Citation Format

Share Document