Intraperitoneal injection of Ginkgo biloba extract enhances antioxidation ability of retina and protects photoreceptors after light-induced retinal damage in rats.

PURPOSE

To investigate the effect of Ginkgo biloba extract EGb 761, a free-radical scavenger, on the antioxidation capability of retina after light-induced retinal damage in rats in an attempt to understand the mechanism by which EGb 761 protects the photoreceptors after light-induced retinal damage.

METHODS

Seventy-two female Sprague-Dawley (SD) rats were evenly randomized into normal control group (NC group), light-induced retinal damage model group (M group), model + normal saline group (MN group), and model + EGb 761 group (ME group). Light-induced retinal damage model was induced via exposure to white light at 2740 +/- 120 lux for 6 hr. Rats in MN group and ME group were intraperitoneally injected daily with normal saline and 0.35% EGb 761 (100 mg/kg), respectively, 1 week before and 2 weeks after light exposure. The levels of malondialdehyde (MDA), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) in the retinal tissues were determined 24 hrs after light exposure; photoreceptor apoptosis was detected 4 days after light exposure. One and 2 weeks after light exposure, histopathologic examination was carried out, and the outer nuclear layer (ONL) thickness (number of nuclei) in the superior and inferior retina was counted.

RESULTS

Twenty-four hours after exposure, the MDA levels in the other three groups were significantly higher than that in the NC group (p < 0.05); those in the M and MN groups were similar to each other (p > 0.05); and that of the ME group was significantly lower than those in the M and MN group (p < 0.05). The activities of T-SOD, GSH-Px, and CAT were similar in the M and MN groups (p > 0.05); the activities in the M and MN groups were significantly lower than those in the NC and ME groups (p < 0.05); and the activities in the ME group were significantly higher than those in the M and MN groups (p < 0.05). Four days after exposure, the apoptotic photoreceptors within the ONL in the ME group were obviously fewer than those in the M and MN groups. One week and 2 weeks after exposure, the ONL thickness (number of nuclei) in the ME group was more than that in the M and MN groups but less than that in the NC group.

CONCLUSIONS

Intraperitoneal injection of EGb 761 can enhance the antioxidation ability of retina and partially inhibit the apoptosis of photoreceptors, thus exert a protective effect on photoreceptors.