AVT and IT Systems mediated metabolic effects induced by air exposicion in the gilthead sea bream (Sparus aurata)

Abstract

Arginine vasotocin (AVT) and isotocin (IT) are considered as important players in stress regulation. The present study assesses the response of both vasotocinergic and isotocinergic systems in the gilthead sea bream (Sparus aurata), through their specific receptors (AVTR V1a2-type, AVTR V2-type and ITR), after an acute stress situation. Specimens were exposed to air for 3 min by lifting the wire-net cage out of the tank and put back in their respective tanks after that, being sampled in a time course response (15 min, 30 min, 1, 2, 4 and 8 hours post-stress). Plasma cortisol values increased after few minutes post-exposure, decreasing during the experimental time while a metabolic reorganization occurred in both plasmatic and hepatic levels. Thus, an enhancement in hepatic glycogenolysis and lactate production, together with higher plasma glucose and lactate levels, as well as a decrease in free plasma proteins was observed. Acute stress response involves changes in gene expression of both hypothalamic AVT and IT precursor levels as well as in their specific hepatic receptors, which are differentially expressed depending on the receptor type (AVTR V1-type, AVTR 2-type or ITR). This response suggests that activation of both vasotocinergic and isotocinerg ic systems is important during metabolic mobilization induced by an acute stress situation, which is stated, at least, through changes in mRNA expression levels of these genes analyzed.