Journal of Neuroscience, Vol 10, 571-577, Copyright © 1990 by Society for Neuroscience
The role of osmotic pressure and membrane potential in K(+)-stimulated taurine release from cultured astrocytes and LRM55 cells
DL Martin, V Madelian, B Seligmann and W Shain
Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201.
The effects of [K+]o on taurine release from glial cells were studied with
primary cultures of cerebellar astrocytes and with LRM55 cells, a
continuous glial cell line. The characteristics of K(+)-stimulated taurine
release were virtually identical in the 2 cell types. Both cerebellar
astrocytes and LRM55 cells released taurine when stimulated with high-K+
medium prepared by isosmotically substituting KCl for NaCl, but neither
cell type released taurine when stimulated with hyperosmotic high-K+ medium
prepared by adding solid KCl to control medium. The membrane potential of
LRM55 cells was measured by intracellular recording and was insensitive to
changes in [K+]o below 20 mM. LRM55 cells released taurine when stimulated
with nondepolarizing concentrations of K+ (13-22 mM) if the isosmotically
prepared high-K+ medium was used, but the cells did not release taurine
when treated with a depolarizing concentration of K+ (50 mM) if
hyperosmotic high-K+ medium was used. The time course of K(+)- stimulated
taurine release was quite slow, having a time to peak of 10- 15 min. Small
changes (2.5-10%) in the osmolarity of the medium strongly affected taurine
release by cerebellar astrocytes and LRM55 cells. K(+)-stimulated taurine
release from both cell types was inhibited when the osmolarity was
increased with sucrose or NaCl and was enhanced when the osmolarity was
reduced. Similarly, baseline taurine release was suppressed by small
elevations in osmolarity and increased by reduced osmolarity.(ABSTRACT
TRUNCATED AT 250 WORDS)
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