CHANGES IN CLUSTERIN EXPRESSION ASSOCIATED WITH LIGHT-INDUCED RETINALDAMAGE IN RATS

Prolonged periods of high-intensity visible light exposure lead to pho toreceptor cell degeneration, but the mechanism of damage is not under stood. Increased clusterin mRNA levels have been found in several mode ls of apoptosis, as well as in neurodegeneration. We report here that changes in clusterin mRNA levels are also associated with light-induce d retinal damage in adult male albino rats. Animals previously maintai ned in darkness or a weak cyclic light environment were exposed to int ense visible green light for up to 24 h. Some rats were pretreated wit h a synthetic antioxidant, dimethylthiourea (DMTU), which reduces phot oreceptor cell degeneration. Clusterin mRNA steady state levels increa sed with the duration of light exposure in both cyclic light and dark reared animals, suggesting that an apoptotic mechanism may be involved . Animals pretreated with DMTU showed a delay in the initial increase in clusterin mRNA levels, suggesting that oxidative damage is involved in the damage mechanism. However, the incomplete suppression of incre asing steady-state clusterin mRNA levels by DMTU suggests that either oxidative damage triggers a second pathway or multiple damage mechanis ms are induced in the retina by light exposure.