Abstract
Chloride ions subserve many physiological functions, including regulation of cell volume, intracellular pH, fluid secretion, and stabilization of the resting membrane potential. Cl− is absorbed along the length of the gastrointestinal tract via region-specific pathways. The major route is an electroneutral NaCl absorptive pathway involving parallel functioning of the Na+/H+ exchanger and Cl− /HCO3− exchanger. SLC26A3, Cl− /HCO3− exchanger, is highly expressed in colonic epithelial cells, and mutations in the SLC26A3 cause congenital chloride diarrhea. These suggest that SLC26A3 play the role in NaCl absorption in the colon. However, the transport characteristics of SLC26A3 have not been fully studied. Since multiple isoforms of the Cl− /HCO3− exchanger are co-expressed in an intact intestinal cell, complicating the functional analysis of an individual isoform, we generated an N-terminal hemagglutinin epitope-tagged human SLC26A3 construct and expressed transiently in CHO cells by using inducible gene expression systems. Using this system, we have characterized SLC26A3 by measuring of its activity with fluorescent pH-sensitive dye, BCECF and chloride-sensitive dye, MEQ. We measured substrates specificity, inhibitors sensitivity and regulation of pH. We also measure Cl− /HCO3− exchanger activity in the isolated colonocytes to determine the functional expression of SLC26A3 in native tissue. We will discuss the role of SLC26A3 in NaCl absorption in the colon. [J Physiol Sci. 2007;57 Suppl:S45]
