title: Voltage clamp of the cardiac sodium current at 37 degrees C in physiologic solutions.
abstract: The cardiac sodium current was studied in guinea pig ventricular myocytes using the cell-attached patch voltage clamp at 37 degrees C in the presence of 145 mM external sodium concentration. When using large patch pipettes (access resistance, 1-2 M omega), the capacity current transient duration was typically 70 microseconds for voltage clamp steps up to 150 mV. At 37 degrees C the maximum inward sodium current peaked in approximately 200 microseconds after the onset of a clamp step and at this strong depolarization, less than 10% of the sodium current developed during the capacity transient. The sodium current developed smoothly and the descending limb of the current-voltage relationship usually spanned a range of 40 mV. Moreover, currents reduced by inactivation of sodium channels could be scaled to superimpose on the maximum current. Current tails elicited by deactivation followed a monoexponential time course that was very similar for currents of different sizes. Data obtained over a range of temperatures (15 degrees-35 degrees C) showed that the steady-state inactivation and conductance-voltage curves were shifted to more negative voltages at lower temperatures. These results demonstrate the feasibility of investigating the sodium current of mammalian cardiac cells at 37 degrees C in normal physiological solutions.
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
authors.forename: K T
authors.initials: KT
authors.lastname: Murray
authors.forename: T
authors.initials: T
authors.lastname: Anno
authors.forename: P B
authors.initials: PB
authors.lastname: Bennett
authors.forename: L M
authors.initials: LM
authors.lastname: Hondeghem
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology*; D008564:Membrane Potentials; D015222:Sodium Channels / Q000502:physiology*; D013696:Temperature; D016276:Ventricular Function
chemical_list: D015222:Sodium Channels