Seasonal levels of metabolic hormones and substrates in male and female reindeer (Rangifer tarandus)

George A. Bubenik, Dieter Schams, Robert G. White, Janice Rowell, John Blake, Ludek Bartos

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

Seasonal levels of cortisol, growth hormone (GH), insulin like growth factor 1 (IGF-1), glucose, triiodothyronine (T3), free T3, thyroxine and free fatty acids (FFA) were measured every 3 weeks for 54 weeks in the plasma of five adult bulls, and four barren and five pregnant Alaskan reindeer (Rangifer tarandus) cows. Three consecutive samples were taken from each animal. Cortisol levels exhibited wide seasonal variation (9-45 μg/100 ml) without any peak or difference in levels among groups. Rising levels were detected between the 3 consequent samples. Peak GH levels, detected during January and February, were higher in the non-pregnant group (54 ng/ml) than the pregnant (26 ng ml-1) and the male (27 ng ml-1) groups. Low GH levels (2-10 ng ml-1) were recorded between May and September. IGF-1 reached peak levels (715 ng ml-1) in males in August, in non-pregnant females in September (677 ng ml-1), and in the pregnant females in October (505 ng ml-1). Seasonal minima (404 in males, 172 and 93 in pregnant and non-pregnant groups) were detected in February. Glucose was fairly stable throughout the year (100-200 mg/100 ml). A rising levels were found between the three consecutive samples. Triiodothyronine (T3) (2.16-2.30 ng ml-1) peaked in all three groups during the spring and early summer, and minimal levels (0.61-0.97 ng ml-1) were detected from October to January. Conversely, thyroxine or free T3 did not exhibit seasonal variation. FFA fluctuated widely (97-1076 nmol l-1) throughout the year. Only in pregnant females were concentrations more stable (150-460 nmol l-1). Perhaps, because of ad libitum supply of food in captive reindeer, only T3 and GH exhibited pronounced seasonal fluctuations which could be related to the metabolic changes expected during the annual cycle. Copyright (C) 1998 Elsevier Science Inc.

Original languageEnglish
Pages (from-to)307-315
Number of pages9
JournalComparative Biochemistry and Physiology - C Pharmacology Toxicology and Endocrinology
Volume120
Issue number2
DOIs
StatePublished - Aug 1998

Keywords

  • Cortisol
  • Female
  • Free fatty acids
  • Glucose
  • Growth hormone
  • Insulin like growth factor-1
  • Male
  • Pregnancy
  • Reindeer
  • Thyroid hormones

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