Vasotocinergic and isotocinergic systems: their roles in osmotic stress in the gilthead sea bream (Sparus aurata)

Abstract

A role in osmotic stress has been proposed for vasotocinergic and isotocincrgic systems in different fish species. We assessed, in a time course response study (day 0, 12 hours, 1, 3, 7 and 14 days), the changes in hypothalamic pro-Vasotocin and pro-Isotocin mRNA expression, as well as in pituitary arginine vasotocin (AVT) and isotocin (IT) content in gilthead sea bream (S. aurata) submitted to acute transfer from 40 ¿ to different environmental salinities: 40 ¿, low salinity water (LSW, 5 ¿) and high saline water (HSW, 55 ¿). Two osmoregulatory periods could be distinguished consistent with plasma osmolality and metabolic parameters variations: i) an adaptative period during the first days of acclimation (12 hours-3 days) with important changes in these parameters, and ii) a chronic regulatory period (after 3 days of transfer) where osmotic parameters reached homeostasis. Clear modifications were distinguished under hiper- and hypoosmotic environments in hypothalamic pro-vasotocin and pro-isotocin mRNA expression as well as in AVT and IT pituitary storage. Pattern of change in pro vasotocin expression, but not of pro-isotocin mRNA, correlated with plasma cortisol variations, indicating a possible interaction between vasotocinergic and stress systems. Pituitary storage of both hormones presented a faster increase in LSW transferred specimens respect to HSW transferred. Our results suggest a role of both vasotocinergic and isotocinergic systems in the osmoregulatory response of gilthead sea bream (S. aurata) to changes in environmental salinities. Acknowledgements: Study funded by project AGL2010-14876 from MICINN. JAM-S is supported by a predoctoral fellowship (FPU, Reference AP2008-01194) from Ministry of Education (Spain).