The conductance of single cardiac sodium channels from guinea pig depends on the intracellular sodium concentration. |
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Authors: | R Albitz G Droogmans B Nilius |
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Institution: | Medical Academy Erfurt, Germany. |
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Abstract: | 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. |
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