title: Effect of spectral transmittance through red-tinted rodent cages on circadian metabolism and physiology in nude rats.
abstract: Light entrains normal circadian rhythms of physiology and metabolism in all mammals. Previous studies from our laboratory demonstrated that spectral transmittance (color) of light passing through cages affects these responses in rats. Here, we addressed the hypothesis that red tint alters the circadian nocturnal melatonin signal and circadian oscillation of other metabolic and physiologic functions. Female nude rats (Hsd:RH-Foxn1(rnu); n = 12 per group) were maintained on a 12:12-h light (300 lx; 123.0 μW/cm(2); lights on 0600):dark regimen in standard polycarbonate translucent clear or red-tinted cages. After 1 wk, rats underwent 6 low-volume blood draws via cardiocentesis over a 4-wk period. Plasma melatonin levels were low during the light phase (1.0 ± 0.2 pg/mL) in rats in both types of cages but were significantly lower in red-tinted (105.0 ± 2.4 pg/mL) compared with clear (154.8 ± 3.8 pg/mL) cages during the dark. Normal circadian rhythm of plasma total fatty acid was identical between groups. Although phase relationships of circadian rhythms in glucose, lactic acid, pO2, and pCO2 were identical between groups, the levels of these analytes were lower in rats in red-tinted compared with clear cages. Circadian rhythms of plasma corticosterone, insulin, and leptin were altered in terms of phasing, amplitude, and duration in rats in red-tinted compared with clear cages. These findings indicate that spectral transmittance through red-colored cages significantly affects circadian regulation of neuroendocrine, metabolic, and physiologic parameters, potentially influencing both laboratory animal health and wellbeing and scientific outcomes.
authors.affiliation: Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, USA. rdauchy@tulane.edu.
authors.forename: Robert T
authors.initials: RT
authors.lastname: Dauchy
authors.affiliation: Department of Comparative Medicine, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Wren
authors.affiliation: Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Dauchy
authors.affiliation: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Hanifin
authors.affiliation: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Jablonski
authors.affiliation: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Warfield
authors.affiliation: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors.forename: George C
authors.initials: GC
authors.lastname: Brainard
authors.affiliation: Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Hill
authors.affiliation: Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors.forename: Lulu
authors.initials: L
authors.lastname: Mao
authors.affiliation: Comparative Medicine, Tulane University School of Medicine, Tulane, Louisiana.
authors.forename: Lynell M
authors.initials: LM
authors.lastname: Dupepe
authors.affiliation: Department of Comparative Medicine, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors.forename: Tara G
authors.initials: TG
authors.lastname: Ooms
authors.affiliation: Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Blask
mesh_terms: D000818:Animals; D000830:Animals, Laboratory; D001786:Blood Glucose / Q000032:analysis; D002940:Circadian Rhythm / Q000528:radiation effects*; D003345:Corticosterone / Q000097:blood / Q000378:metabolism / Q000502:physiology; D005260:Female; D006799:Housing, Animal; D007328:Insulin / Q000097:blood; D008027:Light; D008550:Melatonin / Q000097:blood / Q000378:metabolism; D051381:Rats; D011923:Rats, Nude / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D007328:Insulin; D008550:Melatonin; D003345:Corticosterone