| Objective: To observe the protective effect of hypoxic preconditioning against light-induced photoreceptor cell degeneration in mice, and investigate the possible mechanism. Methods: BALB/C mice were randomly divided into four groups: control group(CON group),simple hypoxic preconditioning group(SO group),simple light-induced group(SL group) and hypoxic pretreated light-induced group(OL group).The last two groups were divided into 6 hour, 12 hour,36 hour and 7 day sub-groups respectively. All mice were raised in cyclic light environment for 10 days and then kept in darkness for 16 hours before experiment. Mice of SO and OL were kept at reduced oxygen levels (8%O2) in a chamber for 6 hours to established hypoxic preconditioning model. Mice of SL and OL were exposed to 58007200Lux illumination of diffuse white fluorescent light for 3 hours to build a model of light-induced damage. Afterwards, all the mice in each group were extracted to make retinal paraffin and ultrathin sections for light and electronic microscopy observation and analysis the changes in the thickness of the outer nucleus layer. Results: 1. Normal mice have clear layers of retinal structures. The inner and outer segments were in neat and orderly arrangement, and the outer nucleus layer(ONL) arranged sequence, stained evenly. Morphological changes of receptors appeared after light exposure and deteriorated gradually along with the progression of light exposure. The outer nuclear layer became thinner and sparser. The outer segments of optic rods of photoreceptors arranged in a confused order, the structure of membranous disks disorganized. Meanwhile, the outer segments of optic rods of photoreceptors in protected group was found no serious changes.2.Analyzing the thickness of the outer nucleus layer in each group via Photo Analysis System, we found that no significant difference of the thickness changes in the outer nucleus layer beteew CON and SO group(p>0.05);ONL was...
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