Deletion of Slc26a6 alters the stoichiometry of apical Cl-/HCO-3 exchange in mouse pancreatic duct.
To define the stoichiometry and molecular identity of the Cl(-)/HCO(3)(-) exchanger in the apical membrane of pancreatic duct cells, changes in luminal pH and volume were measured simultaneously in interlobular pancreatic ducts isolated from wild-type and Slc26a6-null mice. Transepithelial fluxes of HCO(3)(-) and Cl(-) were measured in the presence of anion gradients favoring rapid exchange of intracellular HCO(3)(-) with luminal Cl(-) in cAMP-stimulated ducts. The flux ratio of Cl(-) absorption/HCO(3)(-) secretion was ∼0.7 in wild-type ducts and ∼1.4 in Slc26a6(-/-) ducts where a different Cl(-)/HCO(3)(-) exchanger, most likely SLC26A3, was found to be active. Interactions between Cl(-)/HCO(3)(-) exchange and cystic fibrosis transmembrane conductance regulator (CFTR) in cAMP-stimulated ducts were examined by measuring the recovery of intracellular pH after alkali-loading by acetate prepulse. Hyperpolarization induced by luminal application of CFTRinh-172 enhanced HCO(3)(-) efflux across the apical membrane via SLC26A6 in wild-type ducts but significantly reduced HCO(3)(-) efflux in Slc26a6(-/-) ducts. In microperfused wild-type ducts, removal of luminal Cl(-), or luminal application of dihydro-4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid to inhibit SLC26A6, caused membrane hyperpolarization, which was abolished in Slc26a6(-/-) ducts. In conclusion, we have demonstrated that deletion of Slc26a6 alters the apparent stoichiometry of apical Cl(-)/HCO(3)(-) exchange in native pancreatic duct. Our results are consistent with SLC26A6 mediating 1:2 Cl(-)/HCO(3)(-) exchange, and the exchanger upregulated in its absence, most probably SLC26A3, mediating 2:1 exchange.
Laboratory of Human Nutrition, Nagoya University Graduate School of Medicine, Japan.
Ying
Y
Song
Akiko
A
Yamamoto
Martin C
MC
Steward
Shigeru B H
SB
Ko
Andrew K
AK
Stewart
Manoocher
M
Soleimani
Bai-Chun
BC
Liu
Takaharu
T
Kondo
Chun-Xiang
CX
Jin
Hiroshi
H
Ishiguro
D000818:Animals; D017920:Antiporters / Q000172:deficiency* / Q000235:genetics*; D001639:Bicarbonates / Q000493:pharmacokinetics*; D002712:Chlorides / Q000493:pharmacokinetics*; D003550:Cystic Fibrosis / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D017353:Gene Deletion; D051379:Mice; D018181:Mice, Inbred CFTR; D018345:Mice, Knockout; D010183:Pancreatic Ducts / Q000166:cytology / Q000378:metabolism*; D000076988:Sulfate Transporters
D017920:Antiporters; D001639:Bicarbonates; D002712:Chlorides; C466900:Slc26a6 protein, mouse; D000076988:Sulfate Transporters