ISSN:
1573-6903
Keywords:
Astrocytes
;
neurons
;
potassium and cations
;
potassium and anions
;
pHi and potassium
;
membrane potential and potassium
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Inastrocytes, as [K+]o was increased from 1.2 to 10 mM, [K+]i and [Cl−]i were increased, whereas [Na+]i was decreased. As [K+]o was increased from 10 to 60 mM, intracellular concentration of these three ions showed no significant change. When [K+]o was increased from 60 to 122 mM, an increase in [K+]i and [Cl−]i and a decrease in [Na+]i were observed.Inneurons, as [K+]o was increased from 1.2 to 2.8 mM, [Na+]i and [Cl−]i were decreased, whereas [K+]i was increased. As [K+]o was increased from 2.8 to 30 mM, [K+]i, [Na+]i and [Cl−]i showed no significant change. When [K+]o was increased from 30 to 122 mM, [K+]i and [Cl−]i were increased, whereas [Na+]i was decreased. Inastrocytes, pHi increased when [K+]o was increased. Inneurons, there was a biphasic change in pHi. In lower [K+]o (1.2–2.8 mM) pHi decreased as [K+]o increased, whereas in higher [K+]o (2.8–122 mM) pHi was directly related to [K+]o. In bothastrocytes andneurons, changes in [K+]o did not affect the extracellular water content, whereas the intracellular water content increased as the [K+]o increased. Transmembrane potential (Em) as measured with Tl-204 was inversely related to [K+]o between 1.2 and 90 mM, a ten-fold increase in [K+]o depolarized the astrocytes by about 56 mV and the neurons about 52 mV. The Em values measured with Tl-204 were close to the potassium equilibrium potential (Ek) except those in neurons at lower [K+]o. However, they were not equal to the chloride equilibrium potential (ECl) at [K+]o lower than 30 mM in both astrocytes and neurons. Results of this study demonstrate that alteration of [K+]o produced different changes in [K+]i, [Na+]i, [Cl−]i, and pHi in astrocytes and neurons. The data show that astrocytes can adapt to alterations in [K+]o, in such a way to maintain a more suitable environment for neurons.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00966658
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