Rabbit ileal brush-border membrane Cl-HCO3 exchanger is activated by an internal pH-sensitive modifier site.
The purpose of these studies was to look for evidence of a pH-sensitive modifier site on the Cl-HCO3 exchanger on the brush-border membrane in rabbit ileum utilizing membrane vesicles. When internal pH and HCO3 were increased, Cl uptake was stimulated in a sigmoidal fashion consistent with a modifier effect. Increasing internal HCO3 alone did not have a similar effect, and increasing pH alone in the absence of HCO3 resulted in very little uptake of Cl. These results suggested that OH was a poor substrate for the exchanger but that it "activated" the transport of HCO3. Further evidence for this hypothesis was provided by the observation that increasing internal pH also stimulated Cl-Cl exchange. Altering the membrane potential with K and valinomycin had no effect on Cl uptake at high internal pH, suggesting no change in the 1:1 coupling ratio for Cl-HCO3 exchange at high internal pH. These studies provide evidence that there is an internal pH-sensitive modifier site on the Cl-HCO3 exchanger.
Mugharbil
A
A
Department of Medicine, Yale University School of Medicine, New Haven, Connecticut 06510.
Knickelbein
R G
RG
Aronson
P S
PS
Dobbins
J W
JW
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007082:Ileum / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism; D008564:Membrane Potentials; D008871:Microvilli / Q000378:metabolism* / Q000502:physiology; D011817:Rabbits
D001639:Bicarbonates; D002352:Carrier Proteins; D002712:Chlorides; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid