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Tetrodotoxin binding to normal depolarized frog muscle and the conductance of a single sodium channel.

Authors :
Almers, W
Levinson, S R
Source :
Journal of Physiology; May 1975, Vol. 247 Issue: 2 p483-509, 27p
Publication Year :
1975

Abstract

1. We have examined the binding of tritium‐labelled and unlabelled tetrodotoxin to frog twitch muscle. Bio‐assay as well as radioisotope experiments show a saturable component of tetrodotoxin binding with a binding capacity of about 22 p‐mole/g wet wt., and a dissociation constant of about 5 nM. 2. If the observed uptake of tetrodotoxin by muscles represents one‐to‐one binding of the drug to sodium channels, the channel density is about 380 channels/mum2 of a muscle fibre's surface membrane. On the basis of this result and electrical measurements of sodium conductance in frog muscle, we calculate that the conductance of a single sodium channel is of the order of 10(−12) reciprocal ohms. This is one to two orders of magnitude less than previous estimates. 3. We have looked for an effect of membrane depolarization on saturable tetrodotoxin binding, and have found none. This suggests that there is little molecular interaction between the “gating” portion of the sodium channel molecule, and that which binds tetrodotoxin.

Details

Language :
English
ISSN :
00223751 and 14697793
Volume :
247
Issue :
2
Database :
Supplemental Index
Journal :
Journal of Physiology
Publication Type :
Periodical
Accession number :
ejs34428570
Full Text :
https://doi.org/10.1113/jphysiol.1975.sp010943