At intervals of 0, 6, 12, 24 hours, and 1 week after 2-hour intense light exposure, rats were killed in a CO2-saturated chamber, anterior segments were removed, and retina wholemounts were isolated and shock frozen at −80°C within 2 minutes of enucleation. Retinas were later ultrasonically homogenized into 300 μL Ripa buffer containing 50 mM Tris (pH 7.4), 150 mM NaCl, 10 mM EDTA, 0.1% SDS, 1% NP-40, 0.5% sodium deoxycholate, 1 mM Na3VO4, 1 mM NaF, 1 mM EGTA, 1 mM phenylmethylsulfonyl fluoride, and proteinase inhibitor at 4°C. Protein extracts (20 μg protein in each lane) were separated by 12% SDS-PAGE, and the proteins were transferred to a nitrocellulose membrane. The membranes were then blocked and probed with rabbit polyclonal anti-HO-1 (Abcam, Cambridge, UK), anti-p38 (Promega, Madison, WI), anti-p53 (Chemicon, Temecula, CA), anti-cellular FLICE inhibitory protein (c-FLIP; Abcam), and anti-actin (Sigma, St. Louis, MO) antibody at different dilution. A peroxidase-conjugated anti-rabbit secondary antibody (PerkinElmer, Norwalk, CT) was used at a dilution of 1:15,000. Immunoblots were visualized by chemiluminescence (ECL Plus; Amersham Pharmacia Biotech UK, Little Chalfont, Buckinghamshire, UK).