title: The influence of red light exposure at night on circadian metabolism and physiology in Sprague-Dawley rats.
abstract: Early studies on rodents showed that short-term exposure to high-intensity light (> 70 lx) above 600 nm (red-appearing) influences circadian neuroendocrine and metabolic physiology. Here we addressed the hypothesis that long-term, low-intensity red light exposure at night (rLEN) from a 'safelight' emitting no light below approximately 620 nm disrupts the nocturnal circadian melatonin signal as well as circadian rhythms in circulating metabolites, related regulatory hormones, and physi- ologic parameters. Male Sprague-Dawley rats (n = 12 per group) were maintained on control 12:12-h light:dark (300 lx; lights on, 0600) or experimental 12:12 rLEN (8.1 lx) lighting regimens. After 1 wk, rats underwent 6 low-volume blood draws via cardiocentesis (0400, 0800, 1200, 1600, 2000, and 2400) over a 4-wk period to assess arterial plasma melatonin, total fatty acid, glucose, lactic acid, pO2, pCO2, insulin, leptin and corticosterone concentrations. Results revealed plasma melatonin levels (mean ± 1 SD) were high in the dark phase (197.5 ± 4.6 pg/mL) and low in the light phase (2.6 ± 1.2 pg/mL) of control condi- tions and significantly lower than controls under experimental conditions throughout the 24-h period (P < 0.001). Prominent circadian rhythms of plasma levels of total fatty acid, glucose, lactic acid, pO2, pCO2, insulin, leptin, and corticosterone were significantly (P < 0.05) disrupted under experimental conditions as compared with the corresponding entrained rhythms under control conditions. Therefore, chronic use of low-intensity rLEN from a common safelight disrupts the circadian organization of neuroendocrine, metabolic, and physiologic parameters indicative of animal health and wellbeing.
authors: Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, USA. rdauchy@tulane.edu.
authors: Robert T
authors: RT
authors: Dauchy
authors: Department of Comparative Medicine, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors: Melissa A
authors: MA
authors: Wren
authors: Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors: Erin M
authors: EM
authors: Dauchy
authors: Department of Epidemiology, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors: Aaron E
authors: AE
authors: Hoffman
authors: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors: John P
authors: JP
authors: Hanifin
authors: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors: Benjamin
authors: B
authors: Warfield
authors: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors: Michael R
authors: MR
authors: Jablonski
authors: Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
authors: George C
authors: GC
authors: Brainard
authors: Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors: Steven M
authors: SM
authors: Hill
authors: Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors: Lulu
authors: L
authors: Mao
authors: Department of Comparative Medicine, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors: Georgina L
authors: GL
authors: Dobek
authors: Department of Comparative Medicine, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors: Lynell M
authors: LM
authors: Dupepe
authors: Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane, Louisiana, USA.
authors: David E
authors: DE
authors: Blask
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000528:radiation effects*; D003345:Corticosterone / Q000097:blood; D004032:Diet; D006799:Housing, Animal; D008027:Light; D008297:Male; D008550:Melatonin / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley / Q000097:blood / Q000254:growth & development / Q000502:physiology*
chemical_list: D008550:Melatonin; D003345:Corticosterone
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