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Role of Na + ‐HCO 3 ‐ cotransporter NBCe1 (Slc4a4) in colonic pH i regulation and anion transport (893.38)
Author(s) -
Liu Xuemei,
Yu Qin,
Riederer Brigitte,
Tian DeAn,
Tuo Biguang,
Aalkjaer Christian,
Shull Gary,
Seidler Ursula
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.893.38
Subject(s) - cotransporter , crypt , intracellular ph , chemistry , niflumic acid , symporter , enterocyte , intestinal mucosa , homeostasis , ion transporter , biophysics , epithelial polarity , medicine , microbiology and biotechnology , biochemistry , endocrinology , sodium , intracellular , small intestine , transporter , biology , membrane , organic chemistry , gene
Background : The electrogenic Na + ‐HCO3 ‐ cotransporter NBCe1 (Slc4a4) is strongly expressed in intestinal epithelium. Aim and methods : We used miniaturized Ussing chambers and fluorescent pH‐indicator BCECF‐loaded colonic crypts to study the importance of NBCe1 in pH i control, HCO 3 ‐ as well as anion (Cl ‐ and HCO 3 ‐ ) secretory rates in Slc4a4 KO and WT mice. Results : Steady state pH i and pH i ‐recovery was significantly lower in proximal and distal colonic surface/cryptal mouth cells but not in and colonic crypt base cells, which also displayed high expression levels of the electroneutral NBCn1(Slc4a7) (and was significantly lower in slc4a7‐deficient colonic crypt cells). Forskolin‐stimulated HCO 3 ‐ secretory rates were similar between WT and KO mucosa in all intestinal segments. The Cl ‐ ‐dependent luminal alkalinization rate, which is a function of the anion exchanger slc26a3 (DRA) expressed in the colonic surface cells, were strongly decreased after carbonic anhydrase inhibition in the NBCe1‐deficient but not the WT colonic mucosa. Conclusions : In the intestine, the electrogenic NBCe1 is a mechanism to counteract surface enterocyte acid loads that occur with absorptive processes, but is not important for agonist‐induced electrogenic HCO 3 ‐ secretion, possibly because the concomitant K + channel activation reduces the driving for electrogenic Na + ‐HCO3 ‐ cotransport. Grant Funding Source : Supported by DFG Se 13‐4 and 9‐6 to Ursula Seidler