Figure 9. Proteasome activity in retinal lysates of young untreated, vehicle-treated and MTK-treated old mice. Retinal lysates were incubated for 120 minutes with the substrate Z-Gly-Gly-Leu-AMC at RT, and the fluorescence intensity (RFU) of the liberated AMC was measured every 15 minutes. MG-132 is a proteasome inhibitor and served as an assay control (n = 2). The values are represented as the mean ± SEM, n = 7–8. Two-way ANOVA (main factors: group and time) followed by a Dunnett multiple comparison test. ###p < 0.001, young control group vs. old vehicle-treated group; ****p < 0.0001, old MTK-treated group vs. old vehicle-treated group.