Fig. 4. Amino acid inhibition of D-aspartate transport. The ability of the 20 amino acids (each at 5 mmol l^-1) to compete the transport of D-aspartate (as a mixture of 1 µmol l^-1 cold and 30 nmol l^-1 3H-D-aspartate) was examined. Values are a mean of triplicate experiments, plotted as a percentage of D-aspartate transport (fmol cell^-1 h^-1) in the absence of any competing amino acid. Asterisks indicate significant inhibition at the 99% confidence interval. Note that the results for tyrosine (Y) and tryptophan (W) also appeared to give significant inhibition, but are not indicated by asterisks due to the acidic conditions required for dissolving these amino acids at 5 mmol l^-1, which skewed the results. Amino acids are indicated by the single letter code. –, control (no competing amino acid).