| First Author | Whittamore JM | Year | 2013 |
| Journal | Am J Physiol Gastrointest Liver Physiol | Volume | 305 |
| Issue | 2 | Pages | G172-84 |
| PubMed ID | 23660504 | Mgi Jnum | J:204021 |
| Mgi Id | MGI:5529417 | Doi | 10.1152/ajpgi.00084.2013 |
| Citation | Whittamore JM, et al. (2013) Sulfate secretion and chloride absorption are mediated by the anion exchanger DRA (Slc26a3) in the mouse cecum. Am J Physiol Gastrointest Liver Physiol 305(2):G172-84 |
| abstractText | Inorganic sulfate (SO(4)(2)(-)) is essential for a multitude of physiological processes. The specific molecular pathway has been identified for uptake from the small intestine but is virtually unknown for the large bowel, although there is evidence for absorption involving Na(+)-independent anion exchange. A leading candidate is the apical chloride/bicarbonate (Cl(-)/HCO(3)(-)) exchanger DRA (down-regulated in adenoma; Slc26a3), primarily linked to the Cl(-) transporting defect in congenital chloride diarrhea. The present study set out to characterize transepithelial (3)(5)SO(4)(2)(-) and (3)(6)Cl(-) fluxes across the isolated, short-circuited cecum from wild-type (WT) and knockout (KO) mice and subsequently to define the contribution of DRA. The cecum demonstrated simultaneous net SO(4)(2)(-) secretion (-8.39 +/- 0.88 nmol.cm(-)(2).h(-)(1)) and Cl(-) absorption (10.85 +/- 1.41 mumol.cm(-)(2).h(-)(1)). In DRA-KO mice, SO(4)(2)(-) secretion was reversed to net absorption via a 60% reduction in serosal to mucosal SO(4)(2)(-) flux. Similarly, net Cl(-) absorption was abolished and replaced by secretion, indicating that DRA represents a major pathway for transcellular SO(4)(2)(-) secretion and Cl(-) absorption. Further experiments including the application of DIDS (500 muM), bumetanide (100 muM), and substitutions of extracellular Cl(-) or HCO(3)(-)/CO(2) helped to identify specific ion dependencies and driving forces and suggested that additional anion exchangers were operating at both apical and basolateral membranes supporting SO(4)(2)(-) transport. In conclusion, DRA contributes to SO(4)(2)(-) secretion via DIDS-sensitive HCO(3)(-)/SO(4)(2)(-) exchange, in addition to being the principal DIDS-resistant Cl(-)/HCO(3)(-) exchanger. With DRA linked to the pathogenesis of other gastrointestinal diseases extending its functional characterization offers a more complete picture of its role in the intestine. |
