ACTH administration stimulates both cortisol and aldosterone secretion in fasting northern elephant seals (LB776)
Abstract
During molting, northern elephant seals exhibit substantial alterations in circulating cortisol concentrations, probably to facilitate pelage synthesis while fasting. How these changes influence the hypothalamic‐pituitary‐adrenal (HPA) axis and the stress response, however, is not known. To investigate the modulation of the HPA axis during molting, we administered ACTH (25 units, intramuscularly) to sixteen juvenile elephant seals at the beginning (n=6), middle (n=5), and end (n=5) of their spring molting period in a cross‐sectional study design. Blood samples were collected immediately before, and then periodically for 2.5 hrs after, ACTH administration. We quantified circulating concentrations of ACTH, and the responses of cortisol and aldosterone. Both cortisol and aldosterone concentrations markedly increased following stimulation by ACTH and remained elevated for the duration of sampling (linear mixed model, F = 153, 25.3, respectively; p 0.1). Nonesterified fatty acids increased following ACTH administration, suggesting upregulation of lipolysis; however, blood urea nitrogen concentrations increased only marginally, indicating that protein catabolism was less affected by ACTH administration. ACTH is not a strong aldosterone secretagogue in terrestrial mammals but several studies have measured increased aldosterone after ACTH stimulation in marine mammals, indicating its potential importance in osmoregulation during stress in these species. Cortisol and aldosterone increased in parallel following ACTH stimulation but the slope of this relationship varied among the study groups. This suggests that the release of these hormones is closely coupled in this species and possibly other marine mammals.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 01, 2014
- Source ID
- 10.1096/fasebj.28.1_supplement.lb776
Entities
People
- Cory D Champagne
- Daniel E Crocker
- Dorian S. Houser
- Mike Tift
Organizations
- National Marine Mammal Foundation
- Office of Naval Research
- Sonoma State University