Figure 4. mRNA levels of DNA repair enzymes are decreased in aged retinal pigment epithelium and choroid. Comparisons of the mRNA levels of DNA repair enzymes: OGG1 (A), MYH (B), TDG (C) and NTH1 (D), in mouse retinal pigment epithelium (RPE) and choroid at different ages 18s mRNA was used as internal standard for normalization. The expression levels of OGG1 were decreased at 18 month (p=0.01, n=6), but showed no difference at 12 month (p=0.73, n=6) and at 24 month (p=0.07, n=6) as compared with the 4 month group (n=5) (A). The expression levels of MYH were decreased at 18 month (p=0.001, n=6) and at 24 month (p=0.007, n=6), but showed no difference at 12 month (p=0.87, n=6), compared with the 4 month group (B). The expression levels of TDG were decreased at 18 month (p<0.0001, n=6) and at 24 month (p=0.03, n=6), but showed no difference at 12 month (p=0.35, n=6), compared with the 4 months group (C). The expression levels of NTH1 were not different at all ages tested (p>0.05, n=6; Panel D). Values are the mean ±SEM.