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Dose‐Dependent, K + ‐Stimulated Efflux of Endogenous Taurine from Primary Astrocyte Cultures Is Ca 2+ ‐Dependent
Author(s) -
Philibert Robert A.,
Rogers Keith L.,
Allen Albert J.,
Dutton Gary R.
Publication year - 1988
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1988.tb04844.x
Subject(s) - taurine , efflux , astrocyte , extracellular , medicine , endocrinology , egta , endogeny , chemistry , amino acid , biology , biochemistry , calcium , central nervous system
The K + ‐stimulated efflux of endogenous taurine from primary rat cerebellar astrocyte cultures prepared from 7–9‐day‐old rats was studied at 16–18 days in vitro using HPLC analysis. Taurine efflux was dose‐dependent at K + concentrations between 10 m M and 80 m M , with an EC 50 of approximately 50 m M . Maximum stimulation of efflux above basal levels ranged from 56% at 10 m M K + (204 pmol/min/mg protein) to 470% at 80 m M K + (960 pmol/min/mg protein). Removal of Ca 2+ from the buffer and the addition of either 1 m M EGTA or 10 m M Mg 2+ abolished K. + ‐stimulated efflux. Taurine efflux peaked and fell in parallel with the K + concentration, but with an approximate lag of 3–5 min. The time course and amount of preloaded [ 3 H]taurine released did not differ significantly from that seen for endogenous efflux. Basal taurine efflux varied inversely with the extracellular concentration of Ca 2+ over the concentration range 0–5.0 m M . The observed Ca 2+ dependence is consistent with a role for Ca 2+ in the regulation of taurine release. Furthermore, taurine release from astrocytes in response to elevated K + may reflect a neuromodulatory role for this amino acid in the CNS.