Evidence for the onset of feedback regulation of cortisol in larval summer flounder
Document Type
Article
Date of Original Version
10-12-2007
Abstract
We investigated the functional development of feedback regulation of cortisol levels during early development in a marine teleost, summer flounder, using a novel pharmaceutical approach. Larvae were immersed for 4 h in the glucocorticoid agonist dexamethasone (20 μM) and/or the glucocorticoid-receptor antagonist RU486 (0.12 μM) at 1, 7, or 21 days after hatching. The hypothesis was that, if feedback regulation were operational, tissue cortisol concentrations would be suppressed by dexamethasone and stimulated by RU486. Whole-body cortisol content of 1-day-old larvae was significantly decreased from 0.32 ng/g body weight (mean) to 0.08-0.12 ng/g by immersion in dexamethasone, RU486, or both, perhaps due to displacement of cortisol from the yolk sac. There were no changes in cortisol content among treatment groups in 7-day-old larvae. The expectations of our hypothesis were met in 21-day-old larvae. Immersion in RU486 increased cortisol content from 0.29 ng/g (control) to 2.00 ng/g, whereas immersion in dexamethasone (with or without RU486) suppressed cortisol to 0.03-0.04 ng/g. The results indicate that a fully functional hypothalamic-pituitary-interrenal axis is established by 3 weeks after yolk-sac resorption, but before the onset of metamorphosis in summer flounder. This is the earliest detection of feedback regulation in a teleost fish. © 2007 Elsevier Inc. All rights reserved.
Publication Title, e.g., Journal
General and Comparative Endocrinology
Volume
154
Issue
1-3
Citation/Publisher Attribution
Veillette, Philip A., Xaymara Serrano, Misty M. Garcia, and Jennifer L. Specker. "Evidence for the onset of feedback regulation of cortisol in larval summer flounder." General and Comparative Endocrinology 154, 1-3 (2007). doi: 10.1016/j.ygcen.2007.05.033.