Noise analysis of the K+ current through the apical membrane of Necturus gallbladder.
Current noise power spectra of the voltage-channel (V = 0) Necturus gallbladder, exposed to NaCl-Ringer's on both sides contained a relaxation noise component, which overlapped with a 1/f alpha noise component, with alpha being about 2. Substitution of all Na+ by K+ on either the serosal or mucosal side increased the relaxation as well as the 1/f alpha noise component considerably. In Necturus gallbladder both noise components are reduced by addition of 10 mM, 2,4,6-triaminopyrimidine (TAP) or 5 mM BA2+ to the mucosal side, as well as by acidification of the mucosal solution to pH 5 and lower. Five mM of tetraethylammonium (TEA+) added to the mucosal solution, abolished K+ relaxation noise and decreased the 1/f alpha noise component. Applying a Cs+ concentration gradient across the epithelium did not yield relaxation noise. However, if Rb+ was substituted for all Na+ on one side, a Lorentzian noise component appeared in the spectrum. Its plateau was smaller than with KCl-Ringer's on the respective side. These data confirm the existence of fluctuating K+ channels in the apical membrane of the Necturus gallbladder. Furthermore it can be concluded that these channels have the permeability sequence K+ greater than Rb+ greater than Cs+. The inhibition of the fluctuations by mucosal acidification indicates the existence of acidic sites in the channel. The single-channel conductance was estimated to be between 6.5 and 40 pS.
D000818:Animals; D004553:Electric Conductivity; D004848:Epithelium / Q000502:physiology; D005704:Gallbladder / Q000502:physiology*; D007473:Ion Channels / Q000378:metabolism*; D008564:Membrane Potentials; D009337:Necturus; D011188:Potassium / Q000378:metabolism* / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D007473:Ion Channels; D013757:Tetraethylammonium Compounds; D012964:Sodium; D011188:Potassium