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Abstract #22289 Published in IGR 10-4
Direct effect of light on 24-h variation of aqueous humor protein concentration in Sprague-Dawley rats
Valderrama CM; Li R; Liu JHExperimental Eye Research 2008; 87: 487-491
Sprague-Dawley rats 10-12 weeks of age were entrained to a standard light-dark cycle with lights turned on at 6 a.m. and off at 6 p.m. Variations of 24-h aqueous humor protein concentration were determined. Samples were taken every 4 h (N = 10-14) under the standard light-dark condition at 8 p.m., midnight, 4 a.m., 8 .m., noon, and 4 p.m. Under an acute constant dark condition, when lights were not turned on at 6 .m., samples were collected at 8 a.m., noon, 4 p.m., and 8 p.m. Aqueous humor protein concentrations under the standard light-dark condition were found in the range of 0.305 ± 0.115 mg/ml (mean± SD, N = 10) at midnight to 1.505 ± 0.342 mg/ml (N = 14) at noon. The 3 light-phase protein concentrations were each higher than the 3 dark-phase concentrations. Aqueous humor protein concentrations at 8 a.m., noon, and 4 p.m. under the acute constant dark condition were each higher than the concentrations at 8 p.m. (after both 2 h and 26 h in the dark), midnight, and 4 a.m., demonstrating an endogenously driven 24-h pattern. At 8 a.m., noon, and 4 p.m., protein concentrations were 56-147% higher when exposed to light. Intraocular pressure (IOP) was monitored using telemetry in separate groups of light-dark entrained rats under the standard light-dark condition and the acute constant dark condition. The 24-h IOP pattern was inverse to the 24-h pattern of aqueous humor protein concentration under the standard light-dark condition, and this IOP pattern was not altered by the acute constant dark condition. In conclusion, an endogenously driven 24-h variation of aqueous humor protein concentration occurred in Sprague-Dawley rats with higher concentrations during the light-phase than the dark-phase. This endogenous pattern of protein concentration was accentuated by a direct effect of light, which was unrelated to the 24-h pattern of IOP.
Dr. C.M. Valderrama, Department of Ophthalmology, University of California, San Diego, La Jolla, CA 92093-0946, USA
