title: Potassium channels in Necturus proximal tubule.
abstract: Potassium channels from the apical and basolateral membranes of Necturus proximal tubule were studied using the patch-clamp technique. The conductance of the basolateral channel was dependent on the pipette K+ concentration (apparent Km, 65.5 mM K+; maximum channel conductance, 49.8 pS). The permeability ratio (PK+/PNa+) was approximately 10:1. The fractional open time increased with hyperpolarization, whereas mean open times did not change. Ba2+ (0.1 mM pipette concentration) blocked the channel and reduced the mean open time. The apical K+ channel was activated with depolarization and had a slope conductance of 60 pS in the inside-out configuration (100 mM KCl in the pipette and 2.5 mM KCl in the bath). The K+-Na+ selectivity ratio was 32:1. These different channel types will allow independent control of the apical and basolateral membrane K+ conductances.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D002474:Cell-Free System; D004553:Electric Conductivity; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000502:physiology*; D008564:Membrane Potentials; D009337:Necturus; D011188:Potassium / Q000502:physiology*
chemical_list: D007473:Ion Channels; D011188:Potassium