Abstract
Divalent cations and group-specific chemical modifiers were used to modify sodium efflux in order to probe the molecular structure of sodium channels in dog red blood cells. Hg++, Ni++, Co++, and PCMBS (parachloromercuribenzene sulfonic acid), a sulfhydryl reactive reagent, induce large increases in Na+ permeability and their effects can be described by a curve which assumes 2:1 binding with the sodium channel. The sequence of affinities, as measured by the dissociation constants, reflects the reactivity of these divalent cations with sulfhydryl groups. In addition, the effects of Hg++ and PCMBS can be reversed by the addition of dithiothreitol, an SH-containing compound, to the medium. Much smaller increases in Na+ permeability are produced by Zn++ and the amino-specific reagents, TNBS (2,4,6-trinitrobenzene sulfonic acid) and SITS (4-acetamido-4'-isothiocyano-stilbene-2-2'- disulfonic acid). The Zn++ effect can be described by a curve which assumes bimolecular binding with the channel, and its effect on Na+ permeability can be reversed by the addition of glycine to the medium. The effects of Ni++ and SITS can be completely reversed by washing the cells in 0.16 M NaCl while TNBS binding is partially irreversible. Measurements of mean cell volumes (MCV) indicate that the modifier- induced increases in Na+ permeability are not caused by shrinkage of the cells. It is concluded that the movement of sodium ions through ionic channels in dog red blood cells can be enhanced by modification of amino and sulfhydryl groups. Zn++, TNBS, and SITS increase Na+ permeability by modifying amino groups in the channel while Hg++, Ni++, Co++, and PCMBS act on sulfhydryl groups.
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- CHAN P. C., CALABRESE V., THEIL L. S. SPECIES DIFFERENCES IN THE EFFECT OF SODIUM AND POTASSIUM IONS ON THE ATPASE OF ERYTHROCYTE MEMBRANES. Biochim Biophys Acta. 1964 Mar 30;79:424–426. [PubMed] [Google Scholar]
- CROSBY W. H., MUNN J. I., FURTH F. W. Standardizing a method for clinical hemoglobinometry. U S Armed Forces Med J. 1954 May;5(5):693–703. [PubMed] [Google Scholar]
- Carter J. R., Jr Role of sulfhydryl groups in erythrocyte membrane structure. Biochemistry. 1973 Jan 2;12(1):171–176. doi: 10.1021/bi00725a028. [DOI] [PubMed] [Google Scholar]
- Good N. E., Winget G. D., Winter W., Connolly T. N., Izawa S., Singh R. M. Hydrogen ion buffers for biological research. Biochemistry. 1966 Feb;5(2):467–477. doi: 10.1021/bi00866a011. [DOI] [PubMed] [Google Scholar]
- Heitmann P. A model for sulfhydryl groups in proteins. Hydrophobic interactions of the cystein side chain in micelles. Eur J Biochem. 1968 Jan;3(3):346–350. doi: 10.1111/j.1432-1033.1968.tb19535.x. [DOI] [PubMed] [Google Scholar]
- Hoffman J. F., Laris P. C. Determination of membrane potentials in human and Amphiuma red blood cells by means of fluorescent probe. J Physiol. 1974 Jun;239(3):519–552. doi: 10.1113/jphysiol.1974.sp010581. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hoffman J. F. The red cell membrane and the transport of sodium and potassium. Am J Med. 1966 Nov;41(5):666–680. doi: 10.1016/0002-9343(66)90029-5. [DOI] [PubMed] [Google Scholar]
- Knauf P. A., Rothstein A. Chemical modification of membranes. I. Effects of sulfhydryl and amino reactive reagents on anion and cation permeability of the human red blood cell. J Gen Physiol. 1971 Aug;58(2):190–210. doi: 10.1085/jgp.58.2.190. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MADDY A. H. A FLUORESCENT LABEL FOR THE OUTER COMPONENTS OF THE PLASMA MEMBRANE. Biochim Biophys Acta. 1964 Sep 25;88:390–399. doi: 10.1016/0926-6577(64)90194-9. [DOI] [PubMed] [Google Scholar]
- Miles P. R., Lee P. Sodium and potassium content and membrane transport properties in red blood cells from newborn puppies. J Cell Physiol. 1972 Jun;79(3):367–376. doi: 10.1002/jcp.1040790307. [DOI] [PubMed] [Google Scholar]
- Parker J. C. Dog red blood cells. Adjustment of density in vivo. J Gen Physiol. 1973 Feb;61(2):146–157. doi: 10.1085/jgp.61.2.146. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Parker J. C. Dog red blood cells. Adjustment of salt and water content in vitro. J Gen Physiol. 1973 Aug;62(2):147–156. doi: 10.1085/jgp.62.2.147. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rega A. F., Rothstein A., Weed R. I. Erythrocyte membrane sulfhydryl groups and the active transport of cations. J Cell Physiol. 1967 Aug;70(1):45–52. doi: 10.1002/jcp.1040700107. [DOI] [PubMed] [Google Scholar]
- Sha'afi R. I., Lieb W. R. Cation movements in the high sodium erythrocyte of the cat. J Gen Physiol. 1967 Jul;50(6):1751–1764. doi: 10.1085/jgp.50.6.1751. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sutherland R. M., Rothstein A., Weed R. I. Erythrocyte membrane sulfhydryl groups and cation permeability. J Cell Physiol. 1967 Apr;69(2):185–198. doi: 10.1002/jcp.1040690209. [DOI] [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]