Abstract
1. When red cells loaded with 24Na are incubated in balanced glucose salt solutions, the removal of external potassium reduces sodium efflux by about one third. Ouabain reduces the residual sodium efflux by about one half.
2. The ouabain-sensitive efflux of sodium into potassium-free solutions is accompanied by an equal ouabain-sensitive influx of sodium.
3. If sodium in the external potassium-free salt solution is progressively replaced with choline, both the ouabain-sensitive sodium efflux and the ouabain-sensitive sodium influx are reduced until, with only 5 mM-Na externally, both become very small.
4. At sodium concentrations intermediate between 140 mM and 5 mM, ouabain-sensitive sodium influx and ouabain-sensitive sodium efflux remain equal within the limits of experimental error. The relation between the magnitude of the ouabain-sensitive sodium exchange and the external sodium concentration is roughly linear.
5. As the external sodium concentration is decreased beyond 5 mM towards zero, ouabain-sensitive sodium efflux increases again.
6. In the presence of 5 mM-K, the ouabain-sensitive sodium efflux is scarcely affected by replacing most of the external sodium with choline.
7. In the presence of ouabain, sodium efflux is unaffected by external potassium and is little affected by replacing external sodium with choline.
8. The results suggest that in the absence of external potassium the ouabain-sensitive transport mechanism catalyses a one-for-one exchange of sodium ions across the cell membrane. The relation between this exchange and Ussing's classical `exchange diffusion' is discussed.
9. The exchange does not occur in the presence of external potassium at physiological concentrations.
10. Calculations of sodium efflux were based on the specific activities of total cell sodium: separate experiments confirmed that these were the same as the specific activities of sodium lost to sodium-free solutions. No evidence of a slowly exchanging sodium fraction was found.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Baker P. F., Connelly C. M. Some properties of the external activation site of the sodium pump in crab nerve. J Physiol. 1966 Jul;185(2):270–297. doi: 10.1113/jphysiol.1966.sp007987. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Chandler W. K., Hodgkin A. L., Meves H. The effect of changing the internal solution on sodium inactivation and related phenomena in giant axons. J Physiol. 1965 Oct;180(4):821–836. doi: 10.1113/jphysiol.1965.sp007733. [DOI] [PMC free article] [PubMed] [Google Scholar]
- GLYNN I. M. Sodium and potassium movements in human red cells. J Physiol. 1956 Nov 28;134(2):278–310. doi: 10.1113/jphysiol.1956.sp005643. [DOI] [PMC free article] [PubMed] [Google Scholar]
- GLYNN I. M. The action of cardiac glycosides on sodium and potassium movements in human red cells. J Physiol. 1957 Apr 3;136(1):148–173. doi: 10.1113/jphysiol.1957.sp005749. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Garrahan P. J., Glynn I. M. Facftors affecting the relative magnitudes of the sodium:potassium and sodium:sodium exchanges catalysed by the sodium pump. J Physiol. 1967 Sep;192(1):189–216. doi: 10.1113/jphysiol.1967.sp008296. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Garrahan P. J., Glynn I. M. The sensitivity of the sodium pump to external sodium. J Physiol. 1967 Sep;192(1):175–188. doi: 10.1113/jphysiol.1967.sp008295. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Garrahan P. J., Glynn I. M. Uncoupling the sodium pump. Nature. 1965 Sep 4;207(5001):1098–1099. doi: 10.1038/2071098a0. [DOI] [PubMed] [Google Scholar]
- Hoffman J. F., Kregenow F. M. The characterization of new energy dependent cation transport processes in red blood cells. Ann N Y Acad Sci. 1966 Jul 14;137(2):566–576. doi: 10.1111/j.1749-6632.1966.tb50182.x. [DOI] [PubMed] [Google Scholar]
- SOLOMON A. K. The permeability of the human erythrocyte to sodium and potassium. J Gen Physiol. 1952 May;36(1):57–110. doi: 10.1085/jgp.36.1.57. [DOI] [PMC free article] [PubMed] [Google Scholar]
- TOSTESON D. C., HOFFMAN J. F. Regulation of cell volume by active cation transport in high and low potassium sheep red cells. J Gen Physiol. 1960 Sep;44:169–194. doi: 10.1085/jgp.44.1.169. [DOI] [PMC free article] [PubMed] [Google Scholar]