Figure 2. Inhibition of human retinal pigment epithelial cell line (ARPE-19) cell proliferation by glucosamine (GlcN), measured with a colorimetric test (WST-1) and cell counting. A: ARPE-19 cells were cultured for 48 h at different concentration of GlcN. The proliferation results are expressed as a mean percentage of control proliferation. B: After 24 h culture, the ARPE-19 cells were exposed to 2.5 mM or 5.0 mM GlcN for 3 days. During this time, the medium was not changed. The ARPE-19 cells were exposed to 2.5 mM or 5.0 mM GlcN with either 10% fetal bovine serum (FBS; C) or 10 ng/ml endothelial growth factor (EGF; D) stimulation for 5 days (the medium with fresh GlcN included was changed daily). The results are the means±SD of five independent experiments. The difference in inhibition of ARPE-19 cell proliferation among various concentrations of GlcN was compared with one-way ANOVA (ANOVA); Tukey’s test was used for post-hoc analyses. * p<0.05, ** p<0.01, and *** p<0.001 versus the control.