Competitive membrane adsorption of Na+, K+, and Ca2+ in smooth muscle cells

A theory for Na+, K+ and Ca2+ competitive adsorption to a charged membrane is used to explain a number of experimental observations in smooth muscle. Adsorption is described by Langmuir isotherms for mono- and divalent cations which in turn are coupled in a self-consistent way to the bulk solution t...

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Bibliographic Details
Published in:The Journal of membrane biology 1981-02, Vol.58 (2), p.115-121
Main Authors: Kolber, M A, van Breemen, C
Format: Article
Language:English
Subjects:
Adsorption
Binding, Competitive
Biological Transport, Active
Calcium - metabolism
Models, Biological
Muscle, Smooth - metabolism
Potassium - metabolism
Sodium - metabolism
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Summary:A theory for Na+, K+ and Ca2+ competitive adsorption to a charged membrane is used to explain a number of experimental observations in smooth muscle. Adsorption is described by Langmuir isotherms for mono- and divalent cations which in turn are coupled in a self-consistent way to the bulk solution through the diffuse double layer theory and the Boltzman equations. We found that the dissociation constants for binding of Na+, K+ and Ca2+ in guinea pig taenia coli are ca. 0.009, 1.0, and 4 X 10(-8) M, respectively. Furthermore, the effect of a Ca2+ pump that maintains free surface Ca2+ concentration constant is investigated. A decrease in intracellular Na+ content results in an increased Ca2+ uptake; part of this uptake is due to an increase in surface-bound Ca2+ in an intracellular compartment which is in contact with the myofilaments. Variations in the amount of charge available to bind Ca2+ and the surface charge density are studied and their effect interpreted in terms of different pharmacological agents.
ISSN:0022-2631
1432-1424
DOI:10.1007/BF01870974