Voltage clamp of the cardiac sodium current at 37 degrees C in physiologic solutions.

Murray KT, Anno T, Bennett PB, Hondeghem LM
Biophys J. 1990 57 (3): 607-13

PMID: 2155034 · PMCID: PMC1280754 · DOI:10.1016/S0006-3495(90)82576-5

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.

MeSH Terms (8)

Animals Cells, Cultured Guinea Pigs Heart Membrane Potentials Sodium Channels Temperature Ventricular Function

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