Noise analysis of the K+ current through the apical membrane ofNecturus gallbladder

Publisher Website
Google Scholar
Abstract
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 α noise component, with α 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 α noise component considerably. InNecturus gallbladder both noise components are reduced by addition of 10mm, 2,4,6-triaminopyrimidine (TAP) or 5mm Ba2+ to the mucosal side, as well as by acidification of the mucosal solution to pH5 and lower. Fivemm of tetraethylammonium (TEA+) added to the mucosal solution, abolished K+ relaxation noise and decreased the 1/f α 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 theNecturus gallbladder. Furthermore it can be concluded that these channels have the permeability sequence K+>Rb+>Cs+. The inhibition of the fluctuation by mucosal acidification indicates the existence of acidic sites in the channel. The singlechannel conductance was estimated to be between 6.5 and 40 pS.