The conductance of single cardiac sodium channels from guinea pig depends on the intracellular sodium concentration.
Currents through DPI 201-106 modified single sodium channels have been measured in cell-free inside-out patches from guinea-pig ventricular myocytes. Single-channel conductance and reversal potential of the sodium channel have been calculated at different intracellular sodium concentrations [( Na+]i) from microscopic I-V curves, which were obtained by application of linear voltage ramps. The relation between the reversal potential and [Na+]i could be fitted with a modified Goldman-Hodgkin-Katz equation with a relative permeability for K+ over Na+ ions of 0.054. The zero-current conductance of the Na channel as a function of [Na+]i shows a plateau value at low Na concentrations, and increases in a sigmoidal manner at higher concentrations. It is concluded that the Na channel can carry outward currents and that its conductance depends on [Na+]i.
Albitz
R
R
Medical Academy Erfurt, Germany.
Droogmans
G
G
Nilius
B
B
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*
D010879:Piperazines; D015222:Sodium Channels; C046261:DPI 201-106; D012964:Sodium; D011188:Potassium