Characterization of Na/K pump current in HL-1 cells

Abstract

Recently HL-1 cells became an important tool in cardiac research due to their unique origin. However, the characteristic physiology of HL-1 cells is still not completely described. Therefore, this study is designed to elucidate the electrophysiological properties of one of the basic transporters: Na/K pump in HL-1 cells by means of whole-cell patch-clamp method. A pipette- and bath- solution content was made in order to minimize the rest of transmembrane conductance. Na/K pump current (I_p) was elicited by the use of two different voltage clamp protocols–square pulses between −120 and 40 mV with 10 mV increment from holding potential −40 mV and ramp pulses with the same voltage range (dV/dt = 0.1 V/s). I_p was identified as ouabain-sensitive time-independent current which is inhibited by ouabain with IC₅₀ = 131.7 μmol/L. Through the applied voltage range I_p was outward current showing similar to I_p of other mammalian cells current/voltage relationship: I_p increase with more depolarizing steps and reach plateau at around 0 mV. Current density obtained from 12 cells varied from 0.18±0.12 pA/pF for −120 mV to 1.70±0.45 pA/pF for depolarization 0 mV (cell capacitance was 39.75±8.26 pF).Based on experimental data it is concluded that electrophysiological properties of Na/K pump in HL-1 culture cells is qualitatively comparable to that in native mammalian cells. [Jpn J Physiol 55 Suppl:S125 (2005)]