A role for basolateral anion exchange in active jejunal absorption of HCO-3.
Isolated short-circuited segments of jejunum from Amphiuma absorbed HCO-3 at a rate determined by the anion composition of the bathing media. The rate of HCO-3 absorption (JHCO-3) measured by pH-stat was high when the major anion was Cl-, Br-, I-, or SO2-(4) but was lower when gluconate or benzene sulfonate (SO-3) was the anion. The disulfonic stilbenes SITS, DIDS, and DNDS at 1 mM reduced JHCO-3 and short-circuit current when added to the serosal bathing medium. Inhibition by SITS was comparable whether Cl-, Br-, or SO2-(4) was the major anion, and SITS produced a small inhibition of JHCO-3 in gluconate-based media and no effect in benzene SO3-based media. Under conditions in which tissue conductance was low SITS lowered tissue conductance further. In Cl- media SITS reduced short-circuit current consistent with inhibition of Cl- absorption as well as HCO-3 absorption. Inhibition of the Cl- current by DIDS was not reversed by washout, although the inhibition of JHCO-3 was reversed. The rate of HCO-3 absorption in gluconate media could be increased by serosal addition of Cl-, Br-, or I-. It is concluded that the process that results in net jejunal HCO-3 absorption entails anion-HCO-3 exchange at the basolateral membrane and is distinct from the basolateral Cl(-)-HCO-3 exchange process involved in Cl- absorption.
D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D000838:Anions; D001639:Bicarbonates / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects; D002712:Chlorides / Q000494:pharmacology; D066298:In Vitro Techniques; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism*; D014562:Caudata
D000838:Anions; D001639:Bicarbonates; D002712:Chlorides; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid