Impact of aroclor 1254 on the osmoregulatory function of the vasotocinergic pathway in the gilthead sea bream (Sparus aurata) after a hyperosmotc challenge

Abstract

The present study assesses the response of vasotocinergic system in the gilthead sea bream (Sparus aurata) after administering the polychlorinated biphenyl (PCB) Aroclor 1254 and submits the fish to a hyperosmotic challenge (transfer from seawater, SW: 38 ppt salinity, to high salinity water, HSW: 55 ppt salinity). Fish were injected intraperitoneally with slow-UHOHDVH LPSODQWV ȝ/āJ-1 body weight) of coconut oil alone (control group) or containing two different doses of $URFORU DQG ȝJāJ-1 body weight). Seven days post-injection, 8 fish of each experimental group were sampled, and the remaining animals were transferred from SW to HSW and sampled 3 days posttransfer. Plasma cortisol values, as an indicator of stress response, and several parameters of the vasotocinergic pathway were assessed: hypothalamic mRNA expression of the arginine vasotocin precursor (avt) and its receptors (avtrv1a and avtrv2), as well as plasma and pituitary Avt values. Our results demonstrated that, among other players of the endocrine cascade, Aroclor 1254 inhibited the stimulation of the Avt system observed after hyperosmotic challenge, further noted by the hypophyseal accumulation of this hormone as well as by its undetectable levels in plasma. In summary this study demonstrates that Aroclor 1254 administration altered vasotocinergic system in S. aurata blocking the endocrine osmoregulatory function.