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Junctional Membrane Uncoupling : Permeability transformations at a cell membrane junction

The permeability of the membrane surfaces where cells are in contact (junctional membranes) in Chironomus salivary glands depends on Ca(++) and Mg(++). When the concentration of these ions at the junctional membranes is raised sufficiently, these normally highly permeable membranes seal off; their p...

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Detalles Bibliográficos
Autores principales: Loewenstein, W. R., Nakas, M., Socolar, S. J.
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1967
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2225755/
https://www.ncbi.nlm.nih.gov/pubmed/6050971
Descripción
Sumario:The permeability of the membrane surfaces where cells are in contact (junctional membranes) in Chironomus salivary glands depends on Ca(++) and Mg(++). When the concentration of these ions at the junctional membranes is raised sufficiently, these normally highly permeable membranes seal off; their permeability falls one to three orders, as they approach the nonjunctional membranes in conductance. This permeability transformation is achieved in three ways: (a) by iontophoresis of Ca(++) into the cell; (b) by entry of Ca(++) and/or Mg(++) from the extracellular fluid into the cell through leaks in the cell surface membrane (e.g., injury); or (c) by entry of these ions through leaks arising, probably primarily in the perijunctional insulation, due to trypsin digestion, anisotonicity, alkalinity, or chelation. Ca(++) and Mg(++) appear to have three roles in the junctional coupling processes: (a) in the permeability of the junctional membranes; (b) in the permeability of the perijunctional insulation; and (c) a role long known— in the mechanical stability of the cell junction. The two latter roles may well be closely interdependent, but the first is clearly independent of the others.