Influence of AVT and cortisol treatment on stress and thyroid pathways in the gilthead sea bream (Sparus aurata)

Trabajo presentado en el 10º Congreso de la Asociación Ibérica de Endocrinología Comparada, celebrado en Castellón del 23 al 25 de septiembre de 2015.The endocrine system could be considered as a complex net of pathways for which an interconnection between some of them cannot be ruled out. Cortisol, the main cortico steroid in teleosts, is the final step on the hypothalamic-pituitary-interrenal axis, and its functions are related to intermediary metabolism, osmotic and ionic regulation, growth, stress and immunity. In turn, the vasotocinergic, homologous to the mammalian vasopressinergic pathways, and thyroid systems have also an important role in several physiological processes in which cortisol plays a role (e.g. osmoregulation, metabolism or stress). The aim of this study was to evaluate the possible interaction between different endocrine axes (vasotocinergic, stress and thyroid pathways) in the gilthead sea bream (Sparus aurata), through assessing the effects of exogenous arginine vasotocin (AVT) and cortisol administration. Specimens acclimated to seawater (38 ‰ salinity) were intraperitoneally implanted with vegetable oil (mixture 5:1 coconut and seeds oils) alone (control) or containing different doses of AVT (0.5 or 1.0 ?μg/g body weight) or cortisol (50?μg/g body weight) and sampled at 12 hours, and 1 and 3 days after injection. Thus, both ormones produced a significant decrease of hypothalamic corticotrophin releasing hormone (CRH) mRNA expression from 12/24 hours onwards, while CRH-binding protein (CRH-BP) mRNA levels did not altered its values in any of the intraperitoneally injected specimens during the time that the experiment lasted. Moreover, AVT and cortisol administration independently produced a significant decrease in thyrotropin-releasing hormone (TRH) gene expression from 12 h post-injection, whereas an up-regulation in thyroid receptor β (TRβ) mRNA expression was observed just 12 h after hormonal administration. Our results clearly suggest that both AVT and cortisol hormones independently co-regulate the functions of these endocrine systems.This study was funded by projects AGL2013-48835-C2-1-R from Ministerio de Ciencia e Innovación (Spain) to JMM.Peer reviewe