Noise analysis of the K+ current through the apical membrane of Necturus gallbladder.
Current noise power spectra of the voltage-clamped (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 10mM 2,4,6-triaminopyrimidine (TAP) or 5 mM of tetraethylammonium (TEA+) added to ification 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 a 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; D002586:Cesium / Q000378:metabolism; D004594:Electrophysiology; D005704:Gallbladder / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008566:Membranes / Q000378:metabolism*; D009337:Necturus; D010539:Permeability; D011188:Potassium / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D012413:Rubidium / Q000378:metabolism; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D007473:Ion Channels; D011743:Pyrimidines; D013757:Tetraethylammonium Compounds; C012070:2,4,6-triaminopyrimidine; D002586:Cesium; D019789:Tetraethylammonium; D012413:Rubidium; D011188:Potassium