Intracellular acidification induces Cl/HCO3 exchange activity in the basolateral membrane of beta-intercalated cells of the rabbit cortical collecting duct.

Abstract

High speed video imaging microscopy and the pH-sensitive fluorophore2',7',-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) were used to examine acid-base functions of beta-intercalated cells of the rabbit cortical collecting duct. The presence of intercalated cells was established and the properties of apical and basolateral acid-base transporters assessed by monitoring cell pH during acid loading and luminal and basolateral ion substitutions. We showed that treatment of beta-intercalated cells with ammonium chloride (20 mm) induced a profound decrease of their intracellular pH from 6.98 +/- 5.93 +/- 0.08. pH recovery occurred after different lag periods ranging between 2 to 15 min (0.22 +/- 0. 04 dpH/dt). We demonstrated that this pH recovery mechanism was independent of basolateral Na+ and apical HCO-3 and K+. It was also not affected by apical and basolateral addition of NEM, by basolateral DIDS and by apical application of the H-KATPase inhibitor SCH28080. The process of pH recovery was however, critically dependent on basolateral HCO-3. These results are best explained by acid-induced insertion and/or activation of chloride-bicarbonate exchangers that are functional properties with their apical analogues.