Differential effects of photophase irradiance on metabolic and urinary stress hormone concentrations in blind and sighted rodents

Abed E. Zubidat, Randy J. Nelson, Abraham Haim

Research output: Contribution to journalArticlepeer-review

Abstract

The effects of different photophase irradiance levels on the daily rhythms of energy expenditure (DEE, calculated from oxygen consumption, VO2) and urinary metabolites of stress hormones in sighted (Microtus socialis) and blind (Spalax ehrenbergi) rodents were compared. Five groups of each species were exposed to different irradiance levels (73, 147, 293, 366, and 498 μWcm2) under short photoperiod (8L:16D) condition with constant ambient temperature 25±2°C for 21 days before assessments. As light intensity increased from 73 μWcm2, both species reduced DEE, especially among M. socialis. Cosinor analysis revealed significant ultradian rhythms in VO2 of M. socialis with period length being inversely related to irradiance level. Conversely, in S. ehrenbergi, robust 24 h VO2 rhythms were detected at all irradiances. In M. socialis, significant 24 h rhythms in urinary output of adrenaline were detected only at 293 μWcm2, whereas for cortisol, unambiguous rhythms were detected at 73 and 147 μWcm2. Distinct adrenaline daily rhythms of S. ehrenbergi were observed at 73 and 293 μWcm2, whereas this species exhibited significant rhythms in cortisol at 147 and 293 μWcm2. Changes in photophase irradiance levels affected stress hormone concentrations in a dose-dependent manner. There were significant negative and positive correlations of M. socialis and S. ehrenbergi stress hormones, respectively, with increasing irradiance. Our results indicate photophase light intensity is another environmental factor that can significantly affect entrainment of mammalian daily rhythms. Both low and high irradiance conditions can trigger stress responses, depending on the species' natural habitat.

Original languageEnglish
Pages (from-to)487-516
Number of pages30
JournalChronobiology International
Volume27
Issue number3
DOIs
StatePublished - Apr 2010

Bibliographical note

Funding Information:
This work was supported by found granted from the United States-Israeli Binational Science Foundation (BSF) to Prof. Haim and Prof. Nelson.

Keywords

  • Arginine vasopressin
  • HPA axis
  • Masking
  • Predation pressure
  • Retinal photoreceptors
  • Stress hormone metabolites
  • Subterranean

ASJC Scopus subject areas

  • Physiology (medical)
  • Physiology

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