Evaluation of the osmoregulatory function of taurine in brain cells.

Homogenous primary cultures of mouse astrocytes and cortical neurons were used to clarify the role of taurine in ion and osmoregulation in the CNS. This study indicates that both neurons and glial cells have uptake systems for taurine. The cell water content does not change during loading of cells with taurine. Chemical analysis indicates that part of the accumulated taurine is metabolized and that the product(s) are stored in the cells. Extracellular taurine (1 mM) has no effect on K+, Na+, Cl-, or Ca2+ movements in astrocytes. However, astrocytes loaded to a taurine content which corresponds a concentration of 60 mM (corresponds to normal mouse cortex levels) show a 50% reduction in their K+ accumulation by carriers and a 100% increase in Ca2+ turnover rates. Movements of Ca2+ and K+ are involved in neurotransmission. It appears that taurine stored in glial cells, has an important effect on ion homeostasis in the CNS and may act indirectly on neuronal excitability.