Fig. 6. Kinetics of downregulation of the melanogenic activities and recovery of basal activity levels 48 hours after the oxidative challenge. Cells were pulsed for 20 minutes with H₂O₂ (0.5 mM) and allowed to recover in complete medium for up to 48 hours. The dopa oxidase () and tyrosine hydroxylase () activities of solubilized extracts were measured. The results shown are the mean±s.d. for three independent experiments. Controls for calculation of the % residual activity were collected with the 8, 16, 24 and 48 hours time points. The inset shows the changes in tyrosinase protein levels at 8 and 48 hours, assessed by western blot with PEP7 as primary antibody, after separation by 12% SDS-PAGE.