Single sodium channels from human ventricular muscle in planar lipid bilayers.
Sodium channels from human ventricular muscle membrane vesicles were incorporated into planar lipid bilayers and the steady-state behavior of single sodium channels were examined in the presence of batrachotoxin. In symmetrical 500 mM NaCl the averaged single channel conductance was 24.7 +/- 1.3 pS and the channel fractional open time was 0.85 +/- 0.04. The activation midpoint potential was -99.5 +/- 3.1 mV. Extracellular tetrodotoxin blocked the channel with a k(1/2) of 414 nM at 0 mV. In 7 out of 13 experiments subconductance states were observed (9.2 +/- 1.2 pS). When sodium chloride concentration was lowered to 100 mM, single channel conductance decreased to 19.0 +/- 0.9 pS, steady-state activation shifted by -17.3 +/- 5.1 mV, tetrodotoxin sensitivity increased to 324 nM, and sub-conductance states were invariably observed in single channel records (7.9 +/- 0.7 pS). In the planar lipid bilayer system the properties of cardiac sodium channels from different species are not very different, but there are significant differences between sodium channels from human heart and from human CNS.
Wartenberg
H C
HC
Klinik und Poliklinik für Anästhesiologie und spezielle Intensivmedizin, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany. UMC803@UNI-BONN.de
Wartenberg
J P
JP
Urban
B W
BW
D000779:Anesthetics, Local / Q000494:pharmacology; D001496:Batrachotoxins / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D006321:Heart / Q000502:physiology*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008051:Lipid Bilayers / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D015222:Sodium Channels / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D016276:Ventricular Function
D000779:Anesthetics, Local; D001496:Batrachotoxins; D008051:Lipid Bilayers; D015222:Sodium Channels; D013779:Tetrodotoxin; D012965:Sodium Chloride