Chloride transport in brush-border membrane vesicles from chick jejunum.
This study sought to characterize the mechanism(s) of Cl- transport across brush-border membrane vesicles (BBMV) isolated from chick jejunum. An inwardly directed proton gradient stimulated chloride (36Cl-) uptake. This uptake was inhibited by SITS and H2-DIDS. pH-gradient-stimulated Cl- uptake was electroneutral, since it was only slightly decreased by voltage clamping the BBMV with K+ and valinomycin. An outwardly directed HCO3- gradient significantly increased chloride uptake in the presence of a pH gradient. pH-driven chloride uptake was reduced by the presence of several anions in the uptake buffer. The rank order of potency for inhibition of pH-driven Cl- uptake was Cl- > SCN- > HCO3- > I- > Glu- > HPO4(2-). In the absence of a pH gradient, chloride was less concentrated inside the vesicles than outside. Chloride uptake under these conditions was stimulated by a positive electrical potential inside the vesicles. This stimulation was inhibited by the addition of several anions outside the vesicles. The order of inhibitory potency was SCN- > I- > Cl- > HCO3- > Glu- > HPO4(2-). The results are consistent with the presence of a Cl-/base exchanger and a chloride conductance pathway in the brush-border membrane of chick small intestine.
Cano
M
M
Departamento de Fisiología y Biología Animal, Facultad de Farmacia, Universidad de Sevilla, Spain.
Vázquez
C M
CM
Ilundáin
A
A
D000818:Animals; D000838:Anions / Q000494:pharmacology; D001639:Bicarbonates / Q000494:pharmacology; D001692:Biological Transport; D002645:Chickens; D002712:Chlorides / Q000493:pharmacokinetics*; D006863:Hydrogen-Ion Concentration; D007583:Jejunum / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism
D000838:Anions; D001639:Bicarbonates; D002712:Chlorides; D011188:Potassium