Uptake of D- and L-serine in C6 glioma cells.

Cultured C6 glioma cells were able to accumulate [3H]D- and [3H]L-serine in a temperature- and Na+-dependent and saturable manner. The kinetic analysis of these accumulation phenomena indicates that the D- or L-serine uptake into the glioma cells might occur by a single-component system with an apparent Km value around 2480 microM (for D-serine) or 110 microM (for L-serine) and a Vmax value around 7 nmol/min per mg protein. The ratio of the L- to D-serine uptake affinity was similar to that previously reported in the astrocytes of rat cerebrum. The inhibition profiles of D- and L-serine uptake by various amino acid and related compounds resembled each other and those of the ASCT-like neutral amino acid transporter. The present findings therefore suggest that C6 glioma cells may accumulate D- and L-serine through a common ASCT-like transporter and provide a useful model for the glial uptake of extracellular D- and L-serine in the brain.