Elevated Maternal Adrenocorticosteroids Alter Adrenal Responsiveness in Weaned Northern Elephant Seals (Mirounga angustirostris)

• Main Author: Jorie N. Carvalho
• Other Authors: Dr. Daniel E. Crocker, Dr. Mackenzie Zippay, Dr. David Ensminger
• Format: Master Thesis
• Language: English
• Published: Sonoma State University 2024
• Subjects: Adrenocortical hormones; Northern elephant seal; Adrenocorticosteroids; Hypothalamic-pituitary-adrenal axis; Nes; Nes’; Elephant Seal; Elephant Seals
• Online Access: https://hdl.handle.net/20.500.12680/6h441175n

Maternal adrenocorticosteroids (ACs) have the potential to alter hypothalamic-pituitary-adrenal (HPA) axis responsiveness in vertebrate offspring. Less is known about adrenal effects from the lactational transfer of ACs in free-ranging mammals. To increase maternal ACs, we repeatedly administered adrenocorticosteroid hormone (ACTH) to six lactating female northern elephant seals (NES) during their final week of lactation, and compared their pups to those of to six females who were not manipulated in any way. Three weeks after weaning, pups from treated and untreated females were challenged with ACTH to stimulate the HPA axis. Our aim was to evaluate the post-natal influence of maternal ACs on adrenal phenotypes in weaned pups. Pups were blood sampled every 30 min for 90 min after ACTH injection. Pups were relocated and blood sampled after 24 hr. Treatment pups had lower baseline cortisol concentrations at initial capture. After ACTH injection, treatment pups had a 26% reduction in their total cortisol response compared to controls, and were quicker to return to near baseline values at 24 h. Aldosterone concentrations were similarly elevated in both groups after injection of ACTH, however only treatment pups returned to baseline at 24 h. These data demonstrate strengthened negative feedback for both adrenal hormones in pups from mothers with HPA axis stimulation. Effects of the ACTH challenge on suppression of thyroid hormones were similar between groups. These findings show the effects of lactational transfer of maternal ACs on offspring adrenal phenotype and suggest the potential for trans-generational maternal stress impacts in capital breeding marine mammals.