Figure 6. Effects of L-phenylalanine and L-tyrosine on m-tyrosine-induced cytotoxicity.

CHO cells were plated on to tissue culture dishes and were incubated for 4 h to allow them to attach to the surface. The cells were then exposed for 7–10 days to the indicated final concentrations of 0.2 mM m-tyrosine alone or 0.2 mM m-tyrosine with either 0.2 mM or 1 mM L-phenylalanine or L-tyrosine in medium A containing 10% foetal bovine serum. The resulting cell colonies were stained with Methylene Blue and were counted. Survival curves were constructed by plotting the surviving fractions of cells. Results are means±S.D. for three independent experiments.