期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：1
页码：211-215
DOI：10.1073/pnas.74.1.211
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The density of sodium channels in mammalian myelinated fibers has been estimated from measurements of the binding of [3H]saxitoxin to rabbit sciatic nerve. Binding both to intact and to homogenized nerve consists of a linear, nonspecific, component and a saturable component that represents binding to the sodium channel. The maximum saturable binding capacity in intact nerve is 19.9 +/- 1.9 fmol-mg wet-1; the equilibrium dissociation constant, Kt, is 3.4 +/- 2.0 nM. Homogenization makes little difference, the maximum binding capacity being 19.9 +/- 1.5 fmol-mg wet-1 with Kt = 1.3 +/- 0.7 nM. These values correspond to a density of about 700,000 sodium channels per node--i.e., about 12,000 per mum2 of nodal membrane. From the difference between the values of maximum saturable binding capacity in intact and homogenized preparation, given the statistical uncertainty of their estimate, it seems that the internodal membrane can have no more than about 25 channels per mum2. The significance of these findings for saltatory conduction and in demyelinating disease is discussed.
