title: Apical membrane chloride/base exchange in the rat proximal convoluted tubule.
abstract: To examine whether Cl/base exchange is present on the apical membrane of the proximal convoluted tubule, cell pH was measured fluorometrically in the in vivo microperfused rat proximal tubule with (2',7')-bis(carboxyethyl)-(5,6)-carboxyfluorescein. The effect of luminal chloride addition was examined in tubules perfused symmetrically with chloride-free solutions. In the absence of inhibitors, luminal chloride addition did not affect cell pH. However, after inhibition of basolateral membrane anion transport with peritubular 4-acetamido-4'-isothiocyano-(2,2')-disulfonic-stilbene (to amplify effects of apical membrane transport on cell pH), luminal chloride addition caused a small cell acidification (delta pHi = 0.02). When 1 mM formate was added to the solutions, luminal chloride addition caused a larger change in cell pH (delta pHi = 0.06) that was inhibited by (4,4')-diisothiocyano-(2,2')-disulfonic-stilbene. This stimulation of Cl/base exchange was not seen with 1 mM acetate addition. These results demonstrate apical membrane Cl/base exchange, a significant fraction of which is dependent on the presence of formate and probably represents Cl/formate exchange.
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000136:Acid-Base Equilibrium; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D001639:Bicarbonates / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001639:Bicarbonates; D002712:Chlorides; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid