Abstract
Frog sartorius muscles were made Na-rich by immersion in K-free sulfate Ringer's solution in the cold. The muscles were then loaded with Na24 and the extracellular space cleared of radioactivity. When such Na-rich muscles were transferred to lithium sulfate Ringer's solution at 20°C, Na efflux was observed to increase with time, to reach a maximum about 15 minutes after the transfer of the muscles to Li2SO4, and then to decline. The decline in efflux from these muscles was proportional to ([Na]i)8 over a considerable range of [Na]i. The membrane potential of Na-rich muscles was about -48 mv in K-free sulfate Ringer's at 4°C but changed to -76 mv in the same solution at 20°C and to -98 mv in Li2SO4 Ringer's at 20°C. By contrast, muscles with a normal [Na]i showed a fall in membrane potential when transferred from K-free sulfate Ringer's to Li2SO4 Ringer's solution. The general conclusions from this study are (a) that Na extrusion is capable of generating an electrical potential, and (b) that increases in [Na]i lead to reversible increases in P Na of muscle fibers.
Full Text
The Full Text of this article is available as a PDF (916.7 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- CAREY M. J., CONWAY E. J., KERNAN R. P. Secretion of sodium ions by the frog's sartorius. J Physiol. 1959 Oct;148:51–82. doi: 10.1113/jphysiol.1959.sp006273. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HOROWICZ P., GERBER C. J. EFFECTS OF SODIUM AZIDE ON SODIUM FLUXES IN FROG STRIATED MUSCLE. J Gen Physiol. 1965 Jan;48:515–525. doi: 10.1085/jgp.48.3.515. [DOI] [PMC free article] [PubMed] [Google Scholar]
- KERNAN R. P. Membrane potential changes during sodium transport in frog sartorius muscle. Nature. 1962 Mar 10;193:986–987. doi: 10.1038/193986a0. [DOI] [PubMed] [Google Scholar]
- KEYNES R. D., SWAN R. C. The effect of external sodium concentration on the sodium fluxes in frog skeletal muscle. J Physiol. 1959 Oct;147:591–625. doi: 10.1113/jphysiol.1959.sp006264. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MULLINS L. J., FRUMENTO A. S. The concentration dependence of sodium efflux from muscle. J Gen Physiol. 1963 Mar;46:629–654. doi: 10.1085/jgp.46.4.629. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MULLINS L. J., NODA K. THE INFLUENCE OF SODIUM-FREE SOLUTIONS ON THE MEMBRANE POTENTIAL OF FROG MUSCLE FIBERS. J Gen Physiol. 1963 Sep;47:117–132. doi: 10.1085/jgp.47.1.117. [DOI] [PMC free article] [PubMed] [Google Scholar]
- SJODIN R. A., HENDERSON E. G. TRACER AND NON-TRACER POTASSIUM FLUXES IN FROG SARTORIUS MUSCLE AND THE KINETICS OF NET POTASSIUM MOVEMENT. J Gen Physiol. 1964 Mar;47:605–638. doi: 10.1085/jgp.47.4.605. [DOI] [PMC free article] [PubMed] [Google Scholar]