Expression and function of Na+HCO3- cotransporters in the gastrointestinal tract.
The stomach, duodenum, colon, and pancreas secrete HCO3- ions into the lumen. Although the importance of HCO3- secretion for the maintenance of mucosal integrity, a normal digestion, and the reabsorption of Cl- has been well established, the molecular nature of the apical and basolateral HCO3- transporting proteins has remained largely unknown. Functional studies have suggested that a Na+HCO3- cotransport system, similar but not identical to the well-characterized Na+HCO3- cotransporter in the basolateral membrane of the kidney proximal tubule, is present in duodenal and colonic enterocytes, pancreatic ducts cells, and gastric cells and involved in HCO3- uptake from the interstitium. This report describes our work towards understanding the molecular nature, cellular origin, and functional relevance of the Na+HCO3- cotransporter(s) in the stomach and intestine and reviews work by others on the function and localization of Na+HCO3- cotransport processes in the gastrointestinal tract.
Seidler
U
U
Medizinische Klinik, Universität Tübingen, 72076 Tübingen, Germany. ursula.seidler@uni-tuebingen.de
Rossmann
H
H
Jacob
P
P
Bachmann
O
O
Christiani
S
S
Lamprecht
G
G
Gregor
M
M
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D005753:Gastric Mucosa / Q000378:metabolism*; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D027982:Sodium-Bicarbonate Symporters
D002352:Carrier Proteins; D027982:Sodium-Bicarbonate Symporters