Tyrosine isomers and hormonal signaling: A possible role for the hydroxyl free radical in insulin resistance

Figure 6 Effect of para-, ortho-, or meta-tyrosine supplementation on the proliferation of cells cultured in medium with or without erythropoietin. A: The time-dependent increase in cell count in medium supplemented with p-Tyr (open bars), o-Tyr (black bars) or m-Tyr (grey bars) (^aP < 0.05 vs p-Tyr cultured cells on the same day; n = 10); B: The alterations in the cell counts after incubation for 3 d in medium containing o- or m-Tyr and the indicated additional amount of para-tyrosine (^bP < 0.001 vs p-Tyr-containing medium; n = 5). The results are expressed as the ratio of the protein content of erythropoietin (EPO) and non-EPO (control) cells (^aP < 0.05 vs p-Tyr cultured cells; n = 10). Comparisons were performed using ANOVA and Bonferroni’s post-hoc test. Republished with permission of S Karger AG, Basel from Mikolás et al[21]. p-Tyr: Para-tyrosine; o-Tyr: Ortho-tyrosine; m-Tyr: Meta-tyrosine.