title: Inhibition of basolateral potassium conductance by taurine in the proximal convoluted tubule.
abstract: The effect of taurine on the electrophysiological properties of the basolateral membrane of the rabbit proximal convoluted tubule was examined. Short-duration isosmotic pulses of 40 mM taurine in the bath solution induced basolateral membrane depolarizations (delta Vbl) of 6.44 +/- 0.5 mV, which were reduced by 58% in absence of Na+. In presence of barium and quinine, delta Vbl values were reduced by 55% in Na(+)-containing bath solutions and were completely abolished in Na(+)-free solutions. Continuous addition of taurine into the bath solutions for a period of 5 min induced 1) a decrease in the partial conductance of the basolateral membrane to K+ (tK) from 0.39 to 0.23; 2) an increase in the partial conductance to Cl- (tcl) from 0.055 to 0.172; 3) a rapid and transient increase of the partial conductance mediated by the Na-HCO3 cotransporter (tNaHCO3) from 0.37 to 0.52, followed by a progressive decrease to 0.29; and 4) a depolarization of the basolateral membrane of 16 mV. The absolute membrane conductance mediated by the Na-HCO3 cotransporter was not initially affected by taurine, whereas that to K (GK) initially decreased by a maximal factor of 2 after 1 min, followed by a partial recovery after 5 min, and that to Cl (GCl) increased by a factor of 4. Addition of taurine after a hypotonicity-induced cell swelling produced an inhibition of GK comparable to the one observed under isotonic conditions. These results demonstrate the presence of an electrogenic Na-dependent transport of taurine and indicate that taurine inhibits GK.
authors.affiliation: Groupe de Recherche en Transport Membranaire, Université de Montréal, Quebec, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Breton
authors.forename: F
authors.initials: F
authors.lastname: Belachgar
authors.forename: M
authors.initials: M
authors.lastname: Marsolais
authors.forename: J Y
authors.initials: JY
authors.lastname: Lapointe
authors.forename: R
authors.initials: R
authors.lastname: Laprade
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000502:physiology; D004553:Electric Conductivity; D004594:Electrophysiology; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000502:physiology*; D011188:Potassium / Q000037:antagonists & inhibitors* / Q000502:physiology*; D011817:Rabbits; D027982:Sodium-Bicarbonate Symporters; D013654:Taurine / Q000494:pharmacology*
chemical_list: D002352:Carrier Proteins; D027982:Sodium-Bicarbonate Symporters; D013654:Taurine; D011188:Potassium