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Vivian Lee, Leandro B. Teixeira, James Deyo, Daniel M. Albert, Richard R. Dubielzig; Phototoxic Retinal Damage From Industry Standard Light In Albino Rats In Carcinogenicity Study With 1,4-Benzenedicarboxylic Acid, Bis (2-ethylhexyl) Ester. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2566.
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To report the retinal changes in albino rats induced from industry standard light exposure, and report these changes in the context of a toxicity study with compound, 1,4-Benzenedicarboxylic acid, bis (2-ethylhexyl) ester (DEHT).
F-344 albino rats were maintained under standard conditions to assess the carcinogenicity of Eastman Plasticizer 168 [1,4-Benzenedicarboxylic acid, bis (2-ethylhexyl) ester (DEHT)]. The rats were exposed to industry standard ambient light for 2 years. DEHT was administered in the diet for 104 weeks at dietary levels of 1500, 6000, and 12000 ppm. At the end of the 2-year period, the eyes were removed and processed for routine histologic evaluation. Each eye was independently and blindly examined for histopathological changes in the retina.
Overall achieved dosages of DEHT were 79, 324, and 666mg/kg/day for males and 102, 418, 901 mg/kg/day for females. Degeneration of the outer nuclear layer of the retina was noted in some degree in all of the eyes, including the control group. Terminal males and females given 6000 and 12000 ppm, however, exhibited an increase in the severity of degenerative changes over terminal control animals. The retina of the female rats also appeared to be more severely affected than the male rats even though the female rats only achieved slightly higher doses of DEHT.
Previous investigators have reported the phototoxic effects on the retina of albino rats that have been exposed to intense light levels for short periods of time as a model for age related macular degeneration. In this study, albino rats demonstrated microscopic changes that are morphologically consistent with photo-induced retinal degeneration resulting from exposure to industry standard illumination. These changes occurred not only in the experiment group but also in the control group. DEHT appeared to potentiate these changes, exhibiting a dose dependent effect on the retinal damage. On subanalysis, gender appeared to have an effect on the phototoxic retinal changes, where female rats exhibited increased degenerative changes over male rats. Increased survivability for high dose females may have contributed to this difference. Therefore, it is highly recommended that studies conducted on albino rats exposed to industry standard illumination for extended periods of time be aware of the retinal changes that may occur, as well as to perform subanalyses with time matched controls and genders since these factors may alter the conclusions of future studies.
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