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The permeability of the sodium channel to organic cations in myelinated nerve.
- Source :
-
The Journal of general physiology [J Gen Physiol] 1971 Dec; Vol. 58 (6), pp. 599-619. - Publication Year :
- 1971
-
Abstract
- The relative permeability of sodium channels to 21 organic cations was studied in myelinated nerve fibers. Ionic currents under voltage-clamp conditions were measured in sodium-free solutions containing the test cation. The measured reversal potential and the Goldman equation were used to calculate relative permeabilities. The permeability sequence was: sodium approximately hydroxylamine > hydrazine > ammonium approximately formamidine approximately guanidine approximately hydroxyguanidine > aminoguanididine >> methylamine. The cations of the following compounds were not measurably permeant: N-methylhydroxylamine, methylhydrazine, methylamine, methylguanidine, acetamidine, dimethylamine, tetramethylammonium, tetraethylammonium, ethanolamine, choline, tris(hydroxymethyl)amino methane, imidazole, biguanide, and triaminoguanidine. Thus methyl and methylene groups render cations impermeant. The results can be explained on geometrical grounds by assuming that the sodium channel is an oxygen-lined pore about 3 A by 5 A in cross-section. One pair of oxygens is assumed to be an ionized carboxylic acid. Methyl and amino groups are wider than the 3 A width of the channel. Nevertheless, cations containing amino groups can slide through the channel by making hydrogen bonds to the oxygens. However, methyl groups, being unable to form hydrogen bonds, are too wide to pass through.
- Subjects :
- Amidines metabolism
Animals
Anura
Biguanides metabolism
Bromides
Carboxylic Acids
Chemical Phenomena
Chemistry
Chlorides metabolism
Choline metabolism
Guanidines metabolism
Hydrazines metabolism
Hydrogen
Hydroxylamines metabolism
Imidazoles metabolism
Membrane Potentials
Methylamines metabolism
Models, Biological
Models, Structural
Neural Conduction
Quaternary Ammonium Compounds metabolism
Rana pipiens
Tetraethylammonium Compounds metabolism
Tromethamine metabolism
Cell Membrane Permeability
Neurons physiology
Sodium physiology
Subjects
Details
- Language :
- English
- ISSN :
- 0022-1295
- Volume :
- 58
- Issue :
- 6
- Database :
- MEDLINE
- Journal :
- The Journal of general physiology
- Publication Type :
- Academic Journal
- Accession number :
- 5315827
- Full Text :
- https://doi.org/10.1085/jgp.58.6.599