title: Properties of single K+ channels in the basolateral membrane of rabbit proximal straight tubules.
abstract: The basolateral membrane of rabbit straight proximal tubules, which were cannulated and perfused on one side, was investigated with the patch clamp technique. Properties of inward and outward directed single K+ channel currents were studied in cell-attached and inside-out oriented cell-excised membrane patches. In cell-attached patches with NaCl Ringer solution both in pipette and bath, outward K+ currents could be detected after depolarization of the membrane patch by about 20-30 mV. The current-voltage (i/V) relationship could be fitted by the Goldman-Hodgkin-Katz (GHK) current equation, with the assumption that these channels were mainly permeable for K+ ions. A permeability coefficient PK of (0.17 +/- 0.04).10(-12) cm3/s was obtained, the single channel slope conductance at infinite positive potential g(V infinity) was 50 +/- 12 pS and the single channel conductance at the membrane resting potential g(Vbl) was 12 +/- 3 pS (n = 4). In cell-excised patches, with NaCl in the pipette and KCl in the bath, the data could also be fitted to the GHK equation and yielded PK = (0.1 +/- 0.01).10(-12) cm3/s, g(V infinity) = 40 +/- 4 pS and g(Vbl) = 7 +/- 1 pS (n = 8). In cell-attached patches with KCl in the pipette and NaCl in the bath, inward K+ channels occurred at clamp potentials less than or equal to 60 mV, whereas outward K+ channel current was detected at more positive voltages. The current-voltage curves showed slight inward rectification.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000502:physiology; D002463:Cell Membrane Permeability; D004553:Electric Conductivity; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000502:physiology*; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism*; D011189:Potassium Chloride; D011817:Rabbits; D012965:Sodium Chloride; D012996:Solutions
chemical_list: D007473:Ion Channels; D012996:Solutions; D012965:Sodium Chloride; D011189:Potassium Chloride; D011188:Potassium; D002118:Calcium