PMID: 1214273Dec 4, 1975Paper

Ionic dependence of sodium currents in squid axons analyzed in terms of specific ion "channel" interactions

The Journal of Membrane Biology
M CohenW J Adelman

Abstract

Inward sodium currents were measured from voltage-clamped giant axons externally perfused with artificial seawater (ASW) solutions containing various concentrations of sodium and potassium ions. The data was analyzed under the assumption that under a constant membrane potential sodium conductance is determined by a specific ion-channel site (SIS) reaction. The sodium current density values were expressed in terms of SIS-reaction rates which were compared, by means of minimization techniques, with those computed for various saturation reaction mechanisms. The following conclusions were drawn: 1) The dependence of peak inward sodium current on external sodium and potassium concentrations can be described in terms of saturation reactions. 2) The experimental data fit well the kinetics of a positive cooperative homotropic reaction, involving at least two allosteric active sites. One of these sites may be catalytic while the other, either catalytic or regulatory. 3) The inhibitory effect of external potassium on inward sodium current, can be described by a reversible competitive or noncompetitive inhibition mechanism. The values of the dissociation constant of the inhibitor-site "complex" (Ki) were found to be close to the external ...Continue Reading

References

Nov 1, 1975·The Journal of General Physiology·B Hille
Jan 1, 1972·Annual Review of Biophysics and Bioengineering·G Ehrenstein, H Lecar
Mar 29, 1973·Biochimica Et Biophysica Acta·S N FishmanM V Volkenstein
Jun 1, 1972·The Journal of General Physiology·B Hille
Feb 1, 1971·The Journal of Physiology·R D KeynesE Rojas
Feb 1, 1968·The Journal of General Physiology·B Hille
Apr 28, 1955·The Journal of Physiology·A L HODGKIN, R D KEYNES
Apr 28, 1955·The Journal of Physiology·A L HODGKIN, R D KEYNES

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Citations

May 1, 1980·Journal of Mathematical Biology·H H Kohler, E Vollmerhaus
Sep 7, 1976·Biochemical and Biophysical Research Communications·C Palfrey, U Z Littauer
Feb 13, 2001·Biophysical Journal·N Ilan, S A Goldstein
Feb 1, 1977·Archives of Biochemistry and Biophysics·R E GibsonR D O'Brien
May 1, 1980·European Journal of Biochemistry·Y JacquesM Lazdunski

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