Cortisol and corticosterone independence in cortisol-dominant wildlife

Lee Koren, Douglas Whiteside, Åsa Fahlman, Kathreen Ruckstuhl, Susan Kutz, Sylvia Checkley, Mathieu Dumond, Katherine Wynne-Edwards

Research output: Contribution to journalArticlepeer-review

78 Scopus citations

Abstract

Species have traditionally been defined as cortisol-dominant or corticosterone-dominant, depending on the glucocorticoid that is reported. To assess the degree of covariance versus independence between cortisol and corticosterone, 245 serum samples belonging to 219 individuals from 18 cortisol-dominant, non-domesticated species (6 mammalian orders) were compared by mass spectrometry. In these samples, which were elevated above baseline, concentration ranges were overlapping for cortisol and corticosterone although cortisol was dominant in every sample except one of 17 bighorn sheep with a corticosterone-biased cortisol-to-corticosterone ratio of 0.17. As expected, cortisol and corticosterone were strongly associated among species (r2=0.8; species with high absolute cortisol tend to have high absolute corticosterone concentrations), with wide variation in the species-average cortisol-to-corticosterone ratio (range 7.5-49) and an even wider ratio range across individuals (0.2-341). However, only 9 out of 13 species with >7 individuals showed a positive association between cortisol and corticosterone among individuals, and repeated measures of the cortisol-to-corticosterone ratio within individuals were weakly associated (CV range 3-136%). We conclude that corticosterone, although at lower concentrations, has the potential to signal independently of cortisol, and should be included in integrated endocrine models of stress responses.

Original languageEnglish
Pages (from-to)113-119
Number of pages7
JournalGeneral and Comparative Endocrinology
Volume177
Issue number1
DOIs
StatePublished - 15 May 2012
Externally publishedYes

Bibliographical note

Funding Information:
We are grateful to Lori Rogers from the Calgary Zoo, Pat Curry from the University of Calgary, and the Scandinavian Brown Bear Project, who were instrumental in collecting the mammalian serum samples. Ella Ng and Lea Bond helped with the glucocorticoid analysis. Kim L. Schmidt and Dr. Andrea De Souza provided valuable comments on the manuscript, and Dr. Eli Geffen provided statistical advice. This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada , the Canadian Foundation for Innovation , Alberta Education and Technology , and the Faculty of Veterinary Medicine at the University of Calgary (K.E.W.E.), as well as a postdoctoral fellowship from the University of Calgary Faculty of Veterinary Medicine (L.K./K.E.W.E.). Preliminary results were presented as a poster at the 2011 Society for Behavioral Neuroendocrinology Conference in Querétaro, Mexico with the support of a trainee travel award to L.K.

Keywords

  • Glucocorticoids
  • LC-MS/MS
  • Mammals
  • SPE
  • Serum
  • Stress

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