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Interaction of deoxycholate with the sodium channel of squid axon membranes.

Interaction of deoxycholate with the sodium channel of squid axon membranes. Deoxycholate can react with sodium channels with a high potency. The apparent dissociation constant for the saturable binding reaction is 2 microM at 8 degrees C, and the heat of reaction is approximately -7 kcal/mol. Four independent test with Na-free media, K-free media, tetrodotoxin, and pancuronium unequivocally indicate that it is the sodium channel that is affected by deoxycholate. Upon depolarization of the membrane, the drug modified channel exhibits a slowly activating and noninactivating sodium conductance. The kinetic pattern of the modified channel was studied by increasing deoxycholate concentration, lowering the temperature, chemical elimination of sodium inactivation, or conditioning depolarization. The slow activation of the modified channel can be represented by a single exponential function with the time constant of 1--5 ms. The modified channel is inactivated only partially with a time constant of 1 S. The reversal potential is unchanged by the drug. Observations in tail currents and the voltage dependence of activation suggest that the activation gate is actually unaffected. The apparently slow activation may reflect an interaction betweem deoxycholate and the sodium channel in resting state. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of General Physiology Rockefeller University Press

Interaction of deoxycholate with the sodium channel of squid axon membranes.

The Journal of General Physiology , Volume 76 (3): 355 – Sep 1, 1980

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References (42)

Publisher
Rockefeller University Press
Copyright
© 1980 Rockefeller University Press
ISSN
0022-1295
eISSN
1540-7748
DOI
10.1085/jgp.76.3.355
Publisher site
See Article on Publisher Site

Abstract

Deoxycholate can react with sodium channels with a high potency. The apparent dissociation constant for the saturable binding reaction is 2 microM at 8 degrees C, and the heat of reaction is approximately -7 kcal/mol. Four independent test with Na-free media, K-free media, tetrodotoxin, and pancuronium unequivocally indicate that it is the sodium channel that is affected by deoxycholate. Upon depolarization of the membrane, the drug modified channel exhibits a slowly activating and noninactivating sodium conductance. The kinetic pattern of the modified channel was studied by increasing deoxycholate concentration, lowering the temperature, chemical elimination of sodium inactivation, or conditioning depolarization. The slow activation of the modified channel can be represented by a single exponential function with the time constant of 1--5 ms. The modified channel is inactivated only partially with a time constant of 1 S. The reversal potential is unchanged by the drug. Observations in tail currents and the voltage dependence of activation suggest that the activation gate is actually unaffected. The apparently slow activation may reflect an interaction betweem deoxycholate and the sodium channel in resting state.

Journal

The Journal of General PhysiologyRockefeller University Press

Published: Sep 1, 1980

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