Skip to main content
NCBI home page
Biophysical Journal logoLink to Biophysical Journal
. 1984 Apr;45(4):693–698. doi: 10.1016/S0006-3495(84)84211-3

Ca2+-activated K+ channels in human red cells. Comparison of single-channel currents with ion fluxes.

R Grygorczyk, W Schwarz, H Passow
PMCID: PMC1434921  PMID: 6326876

Abstract

Exposure of the inner surface of intact red cells or red cell ghosts to Ca2+ evokes unitary currents that can be measured in cell-attached and cell-free membrane patches. The currents are preferentially carried by K+ (PK/PNa 17) and show rectification. Increasing the Ca2+ concentration from 0 to 5 microM increases the probability of the open state of the channels parallel to the change of K+ permeability as observed in suspensions of red cell ghosts. Prolonged incubation of red cell ghosts in the absence of external K+ prevents the Ca2+ from increasing K+ permeability. Similarly, the probability to find Ca2+-activated unitary currents in membrane patches is drastically reduced. These observations suggest that the Ca2+-induced changes of K+ permeability observed in red cell suspensions are causally related to the appearance of the unitary K+ currents. Attempts to determine the number of K+ channels per cell were made by comparing fluxes measured in suspensions of red cells with the unitary currents in membrane patches as determined under comparable ionic conditions. At 100 mM KCl in the external medium, where no net movements of K+ occur, the time course of equilibration of 86Rb+ does not follow a single exponential. This indicates a heterogeneity of the response to Ca2+ of the cells in the population. The data are compatible with the assumption that 25% of the cells respond with Pk = 33.2 X 10(-14)cm3/s and 75% with Pk = 3.1 X 10(-14)cm3/s. At 100 mM external K+ the zero current permeability of a single channel is 6.1 X 10(-14)cm3/s (corresponding to a conductance of 22 pS). Using appropriate values for the probability of a channel in the open state, we estimated that 25% of the cells in the population contain 11-55, and 75% of the cells 1-5 channels per cell that are activated in the time average (20 degrees C, pH 7.6).

Full text

PDF
693

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Barrett J. N., Magleby K. L., Pallotta B. S. Properties of single calcium-activated potassium channels in cultured rat muscle. J Physiol. 1982 Oct;331:211–230. doi: 10.1113/jphysiol.1982.sp014370. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Bodemann H., Passow H. Factors controlling the resealing of the membrane of human erythrocyte ghosts after hypotonic hemolysis. J Membr Biol. 1972;8(1):1–26. doi: 10.1007/BF01868092. [DOI] [PubMed] [Google Scholar]
  3. GARDOS G. The function of calcium in the potassium permeability of human erythrocytes. Biochim Biophys Acta. 1958 Dec;30(3):653–654. doi: 10.1016/0006-3002(58)90124-0. [DOI] [PubMed] [Google Scholar]
  4. Gárdos G., Szász I., Sarkadi B. Effect of intracellular calcium on the cation transport processes in human red cells. Acta Biol Med Ger. 1977;36(5-6):823–829. [PubMed] [Google Scholar]
  5. Hamill O. P., Marty A., Neher E., Sakmann B., Sigworth F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981 Aug;391(2):85–100. doi: 10.1007/BF00656997. [DOI] [PubMed] [Google Scholar]
  6. Heinz A., Passow H. Role of external potassium in the calcium-induced potassium efflux from human red blood cell ghosts. J Membr Biol. 1980 Dec 15;57(2):119–131. doi: 10.1007/BF01868998. [DOI] [PubMed] [Google Scholar]
  7. LaCelle P. L., Rothsteto A. The passive permeability of the red blood cell in cations. J Gen Physiol. 1966 Sep;50(1):171–188. doi: 10.1085/jgp.50.1.171. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Latorre R., Miller C. Conduction and selectivity in potassium channels. J Membr Biol. 1983;71(1-2):11–30. doi: 10.1007/BF01870671. [DOI] [PubMed] [Google Scholar]
  9. Lew V. L., Muallem S., Seymour C. A. Properties of the Ca2+-activated K+ channel in one-step inside-out vesicles from human red cell membranes. Nature. 1982 Apr 22;296(5859):742–744. doi: 10.1038/296742a0. [DOI] [PubMed] [Google Scholar]
  10. Methfessel C., Boheim G. The gating of single calcium-dependent potassium channels is described by an activation/blockade mechanism. Biophys Struct Mech. 1982;9(1):35–60. doi: 10.1007/BF00536014. [DOI] [PubMed] [Google Scholar]
  11. Schwarz W., Passow H. Ca2+-activated K+ channels in erythrocytes and excitable cells. Annu Rev Physiol. 1983;45:359–374. doi: 10.1146/annurev.ph.45.030183.002043. [DOI] [PubMed] [Google Scholar]
  12. Sigworth F. J., Neher E. Single Na+ channel currents observed in cultured rat muscle cells. Nature. 1980 Oct 2;287(5781):447–449. doi: 10.1038/287447a0. [DOI] [PubMed] [Google Scholar]
  13. Simons T. J. Calcium-dependent potassium exchange in human red cell ghosts. J Physiol. 1976 Mar;256(1):227–244. doi: 10.1113/jphysiol.1976.sp011322. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Yingst D. R., Hoffman J. F. Ca-induced K transport in human red blood cell ghosts containing arsenazo III. Transmembrane interactions of Na, K, and Ca and the relationship to the functioning Na-K pump. J Gen Physiol. 1984 Jan;83(1):19–45. doi: 10.1085/jgp.83.1.19. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Biophysical Journal are provided here courtesy of The Biophysical Society

RESOURCES