title: Direct effect of light on 24-h variation of aqueous humor protein concentration in Sprague-Dawley rats.
abstract: Sprague-Dawley rats 10-12 weeks of age were entrained to a standard light-dark cycle with lights turned on at 6 am and off at 6 pm. Variations of 24-h aqueous humor protein concentration were determined. Samples were taken every 4h (N=10-14) under the standard light-dark condition at 8 pm, midnight, 4 am, 8 am, noon, and 4 pm. Under an acute constant dark condition, when lights were not turned on at 6 am, samples were collected at 8 am, noon, 4 pm, and 8 pm. 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 am, noon, and 4 pm under the acute constant dark condition were each higher than the concentrations at 8 pm (after both 2h and 26 h in the dark), midnight, and 4 am, demonstrating an endogenously driven 24-h pattern. At 8 am, noon, and 4 pm, 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.
authors.affiliation: Department of Ophthalmology, University of California, San Diego, La Jolla, CA 92093-0946, USA.
authors.forename: Chad M
authors.initials: CM
authors.lastname: Valderrama
authors.forename: Ruixia
authors.initials: R
authors.lastname: Li
authors.forename: John H K
authors.initials: JH
authors.lastname: Liu
mesh_terms: D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D005136:Eye Proteins / Q000378:metabolism*; D007429:Intraocular Pressure / Q000502:physiology; D008027:Light; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D005136:Eye Proteins