Figure 3. Dependence of taurine and glutamate uptake on extracellular [Na⁺] in cultured astrocytes.

Taurine and glutamate transport rates were measured in primary astrocyte cultures using [³H]taurine and d-[³H]aspartate. Extracellular concentrations of amino acids were adjusted to 10 µM using unlabeled taurine or l-glutamate. To compare glutamate versus taurine uptake, the values were normalized to uptake levels under basal conditions ([Na⁺]_o = 135 mM). Note that under basal conditions absolute d-[³H]aspartate uptake rate (nmols/mg protein) was ∼5-fold higher compared to taurine. Data are the mean values ±SEM of three experiments from each group.