title: A chloride conductance exhibiting bicarbonate conductivity in renal inner medullary collecting duct cells.
abstract: The anion conductance in primary cultures of rat inner medullary collecting duct cells was studied using perforated-patch whole-cell clamp technique. Depolarizations above 0 mv induced an outward anionic current with a time-dependent activation (Iovt) exhibiting a similar conductivity to Cl- and HCO3-. Iovt showed half-maximal activation around 32 mV with a slope factor of 23 mV, and showed a voltage-dependent activation time course that was well fitted by a sum of two exponential functions. Iovt was potentiated when external pH or external Ca2+ was increased and was blocked by external DIDS, DPC and furosemide. These characteristics of Iovt resemble that of the ClC-K1 channels mediated currents; however, anion substitution studies showed that Iovt exhibits a Br->Cl->I->NO3- conductivity sequence, different from that observed in the ClC-K1 channels-mediated conductance. We suggest that, in inner medullary collecting duct cells, ClC-K channels of an unidentified type give rise to this Cl- and HCO3- conductance. This is the first study of a channel-mediated HCO3- current in kidney tubular cells.
authors.affiliation: Department of Physiology, Faculty of Medicine, The National Autonomous University of Mexico, Mexico City, Mexico. jjboliv@unam.mx.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Bolívar
authors.forename: César O
authors.initials: CO
authors.lastname: Lara-Figueroa
authors.forename: Ramón H
authors.initials: RH
authors.lastname: Martínez-Mayorquin
authors.forename: Florencio
authors.initials: F
authors.lastname: Monroy-Romero
authors.forename: Gabina
authors.initials: G
authors.lastname: Arenas
mesh_terms: D000818:Animals; D000838:Anions; D001639:Bicarbonates / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D018118:Chloride Channels / Q000737:chemistry; D002712:Chlorides / Q000378:metabolism*; D004553:Electric Conductivity; D005665:Furosemide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D000838:Anions; D001639:Bicarbonates; D018118:Chloride Channels; D002712:Chlorides; D005665:Furosemide; D002118:Calcium