Interaction of Cl- and other halogens with Cl- transport systems in rabbit cortical collecting duct

We have reported that in the rabbit cortical collecting duct (CCD) we can identify electrophysiologically three distinct cell types; the collecting duct (CD) cell and the alpha- and beta-intercalated (IC) cell. To further characterize the Cl- transport properties of each cell type, we examined the interaction between Cl- and other halogens or SCN- in the isolated and perfused CCD by intracellular microelectrode impalement. The rapid depolarization of the basolateral membrane potential (VB) caused by replacement of bath Cl- with each anion revealed that the sequences of apparent halogen selectivity for the basolateral Cl- conductance were similar in all three cell types. The ranking of Cl- > Br- > F- > I- corresponds to the sequence 5 of Eisenman's series, indicating "strong" interaction of the anions with the selectivity site. The basolateral Cl- conductance of these three cell types may share common characteristics, although I- permeability is less in IC cells than in CD cells. Hyperpolarization of the basolateral membrane of the beta-IC cell upon reduction of luminal Cl- reflects alterations in either Cl- entry across the apical membrane, or Cl- exit across the basolateral membrane, or both. Luminal Cl- replacement with each anion showed that the sequence of the hyperpolarization of the basolateral membrane was I- >> cyclamate = SCN- > F- > Br-, suggesting that I-inhibits either apical Cl- entry or basolateral Cl- exit. On the other hand, in the CD cell reduction of the perfusate Cl- by replacement with each anion caused the basolateral membrane to hyperpolarize with a different ranking: cyclamate = F- > I- = SCN- > Br-.(ABSTRACT TRUNCATED AT 250 WORDS)