Objective:To observe the inhibited effect and its mechani sm of estro gen on lightinduced apoptosis of retinal photoreceptor cells. Methods:Twenty female Sprague-Dawley rats were randomly divided into two groups: ovariectomized (OV) group and OV and estrogen (E2) replacement (OV+E2) group, with 10 rats in each group. All of the rats were exposed to the cyclic illumination under 12 hou r light and 12 hour dark condition with the light intensity of (600 plusmn;35.4) lx ( a total of 14 times). All of the right eyes were extracted and the thickness of r etinal outer nuclear layer (ONL) was measured. Terminal deoxynucleotidyl Transfe rasemediated dUTP nick end labeling (TUNEL) method was used to evaluate positi v e apoptosis cells in ONL. The expression of nitric oxide synthase (NOS) in retin al cells was detected by immunohistochemistry with image analysis method. Results:The thickness of ONL in OV group was obviously thinner than that in the OV+ E2 group. The number of positive apoptosis of the cells was (0.0275 plusmn;0.0069) c el ls/ mu;m2 in OV group and (0.0162 plusmn;0.0054) cells/ mu;m2 in OV+E2group; the di fferen ce between the two groups was significant (t=4.1370，P=0.0012). The values o f in tegral optical density of NOS positively stained cells in retinal inner nuclear layer was (0.3675 plusmn;0.0662) in the OV group and (0.2941 plusmn;0.0350) in OV+E2 group ; the difference between the two groups was significant (t=3.4885, P=0.0031). Conclusion:Estrogen can protect retina from light injuries by regu lating NOS synthesis and inhibiting apoptosis of photoreceptor cells.

Citation： CHEN Xiaohu,ZHANG Junjun,DAI Yan. Protective effects of estrogen on retina from the light injury. Chinese Journal of Ocular Fundus Diseases, 2007, 23(5): 324-326. doi: Copy