Figure 1. Light exposure increases the level of HO-1 in photoreceptors and RPEs. 661W cells/ARPE-19 cells were cultured in dark conditions or exposed to 1500 Lux light for 1–3 days. The level of HO-1 protein in the whole cell lysate was determined with western blotting, and β-actin was referenced as an internal control. Three independent experiments are conducted two weeks apart. The results are presented as the mean± SEM. n (per group) =3, **P < 0.01.