Arginine Vasotocin and Cortisol Co-regulate Vasotocinergic, Isotocinergic, Stress, and Thyroid Pathways in the Gilthead Sea Bream (Sparus aurata)

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2019-03Department
BiologíaSource
FRONTIERS IN PHYSIOLOGY, 10, 261Abstract
In teleosts, a complex interaction between several endocrine axes modulates
physiological functions related to metabolism, stress, and osmoregulation. Although
many studies in fish underline the interconnection between the hypothalamic–
pituitary–interrenal (HPI) and hypothalamic–pituitary–thyroid (HPT) endocrine axes, their
relationship with the vasotocinergic and isotocinergic systems remains unknown. The
aim of the present study is therefore to shed light on the potential cross-regulations
between HPT, HPI, and the vasotocinergic and isotocinergic axes in gilthead sea bream
(Sparus aurata) at hypothalamic, hypophyseal, and plasma levels. Sea breams were
administered with intraperitoneal slow-release implants containing different doses of
vasotocin (the active peptide in vasotocinergic system) or cortisol (the last component
of HPI axis). Plasma osmolality was higher in active neuropeptides vasotocin (Avt)-
treated fish, indicating an osmoregulatory function of this hormone. Low concentrations
of Avt increased hypothalamic arginine vasotocin precursor (avt) mRNA levels and
increased Avt storage in the pituitary. Avt treatment down-regulated hypothalamic
arginine vasotocin receptor v1a-type (avtrv1a), suggesting a negative paracrine coregulation
of the HPI axis due to the close location of avtrv1a and adrenocorticotropin
hormone (Acth) cells in the anterior pituitary. Furthermore, the up-regulation observed
in arginine vasotocin receptor v2-type (avtrv2) suggests their involvement in metabolic
and cortisol-related pathways in the hypothalamus. The decrease in isotocin (It) pituitary
storage and the up-regulation of it receptor, observed in the Avt-treated group, reinforce
the idea of an interconnection between the vasotocinergic and isotocinergic systems.
Cortisol and Avt administration each inhibited the HPI axis, down-regulating crh gene
expression in the absence of variations in corticotropin releasing hormone binding protein (crhbp). Finally, both hormonal treatments activated the HPT axis via upregulation
of trh and down-regulation of thrb. Our results provide evidence for strong
interactions among the Avt/It, HPI, and HPT axes of marine teleosts, particularly at the
hypothalamic level.
Subjects
arginine vasotocin; cortisol; Crh; isotocin; receptors; Sparus aurata; stress; thyroid systemCollections
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