title: Chloride channels in apical membrane of primary cultures of rabbit distal bright convoluted tubule.
abstract: Using the patch clamp technique on the apical membrane of primary cultures of rabbit distal bright convoluted tubule cells (DCTb), two types of Cl- channel were identified. A small channel of 9 pS was observed in 9% of the patches. Cells pretreated with 1 mM 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) or 5 microM forskolin increased the expression of Cl- channels by 26 and 37%, respectively. In cell-attached and excised inside-out patches, the current-voltage (I-V) relationships of the 9-pS channel were linear. In only 1 out of 47 active patches was the small-conductance Cl- channel still active 1 h after membrane excision. The addition of 0.1 microM of the catalytic subunit protein kinase A with 2 mM ATP to the cytoplasmic side restored channel activity in 8 out of 15 excised membrane patches. In 5 out of 467 patches of stimulated or nonstimulated cells, a larger Cl- conductance of 30 pS was also recorded. In excised inside-out patches this channel outwardly rectified and was activated by strong depolarization. In cultured DCTb cells, the small-conductance, cAMP-activated Cl- channel shares many properties with the cystic fibrosis transmembrane conductance regulator. Our results suggest that at least the small-conductance channel may participate in Cl- secretion across the apical membrane of DCTb in primary culture. This secretion may increase the rate of the apical Cl-/HCO3- exchange indirectly by enhancing the inwardly-directed Cl- gradient.
authors.affiliation: Département de Biologie Cellulaire et Moléculaire, Centre d'Etudes de Saclay, Gif sur Yvette, France.
authors.forename: V
authors.initials: V
authors.lastname: Poncet
authors.forename: M
authors.initials: M
authors.lastname: Tauc
authors.forename: M
authors.initials: M
authors.lastname: Bidet
authors.forename: P
authors.initials: P
authors.lastname: Poujeol
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002384:Catalysis; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D000242:Cyclic AMP / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000494:pharmacology; D004553:Electric Conductivity; D007686:Kidney Tubules, Distal / Q000166:cytology / Q000378:metabolism*; D008297:Male; D011817:Rabbits
chemical_list: D018118:Chloride Channels; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases