c-Fos protein in photoreceptor cell death after photic injury in rats

PURPOSE. To examine the involvement of c-Fos protein in light-induced photoreceptor cell death in rats. METHODS. Thirty-two Lewis albino rats were exposed to green fluorescent light (480-520 nm) of 300 to 320 foot-candles (3228-3443.2 lux) for 3 hours, allowed to recover in the dark, and euthanatized at O, 1, 3, 6, 12, 24, or 96 hours after light exposure. c-Fos was detected immunohistochemically and nicked DNA by in situ TdT-dUTP terminal nick-end labeling (TUNEL). Double labeling of c-Fos and DNA nicks was also performed. RESULTS. There was a time-dependent change in the number of c-Fos-positive photoreceptor nuclei after light injury, which parceled the change in the number of TUNEL-positive nuclei. The temporal and spatial appearance of these nuclei also matched the appearance of pyknotic nuclei of the outer nuclear layer. Double-labeling study revealed that some c-Fos-positive nuclei were also TUNEL-positive nuclei. CONCLUSIONS. There was an acute accumulation of c-Fos protein in photoreceptor associated with cell death. This study further supports other studies showing that c-Fos is linked to apoptotic photoreceptor cell death.