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REPORTS
1Laboratory of Human Nutrition, Nagoya University Graduate School of Medicine, Nagoya, Japan; 2Department of Pharmacology, Institute of Gastroenterology, Yonsei University College of Medicine, Seoul, Korea; and Departments of 3Medicine and 4Surgery, University of Cincinnati and 5Veterans Administration Medical Center, Cincinnati, Ohio
Submitted 30 June 2006 ; accepted in final form 8 August 2006
ABSTRACT
The role of Slc26a6 (PAT1) on apical Cl/HCO3 exchange and bicarbonate secretion in pancreatic duct cells was investigated using Slc26a6 null and wild-type (WT) mice. Apical Cl/HCO3 exchange activity was measured with the pH-sensitive dye BCECF in microperfused interlobular ducts. The HCO3-influx mode of apical [Cl]i/[HCO3]o exchange (where brackets denote concentration and subscripts i and o denote intra- and extracellular, respectively) was dramatically upregulated in Slc26a6 null mice (P < 0.01 vs. WT), whereas the HCO3-efflux mode of apical [Cl]o/[HCO3]i exchange was decreased in Slc26a6 null mice (P < 0.05 vs. WT), suggesting the unidirectionality of the Slc26a6-mediated HCO3 transport. Fluid secretory rate in interlobular ducts were comparable in WT and Slc26a6 null mice (P > 0.05). In addition, when pancreatic juice was collected from whole animal in basal and secretin-stimulated conditions, neither juice volume nor its pH showed differences between WT and Slc26a6 null mice. Semiquantitative RT-PCR demonstrated more than fivefold upregulation in Slc26a3 (DRA) expression in Slc26a6 knockout pancreas. In conclusion, these results point to the role of Slc26a6 in HCO3 efflux at the apical membrane and also suggest the presence of a robust Slc26a3 compensatory upregulation, which can replace the function of Slc26a6 in pancreatic ducts.
cystic fibrosis transmembrane regulator; cystic fibrosis; sodium bicarbonate exchanger; HCO3 secretion; HCO3 transporters; downregulated in adenoma; putative anion transporter 1
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