Evidence that dopamine is involved in neuroendocrine regulation, gill intracellular signaling pathways and ion regulation in Litopenaeus vannamei

The transport of ions and ammonia in the gills may be regulated by neuroendocrine factors, in order to explore the regulation mechanism of dopamine (DA), hemolymph neuroendocrine hormones, gill intracellular signaling pathways, ion and ammonia transporters, as well as hemolymph osmolality and ammonia concentration were investigated in Litopenaeus vannamei after 10−7 and 10−6 mol shrimp−1 DA injection. The data displayed a significant increase in crustacean hyperglycemic hormone (CHH) concentration at 1-12 h and a transient significant decrease in corticotrophin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH) and cortisol concentrations under DA stimulation. The up-regulation of guanylyl cyclase (GC) mRNA, cyclic guanosine monophosphate (cGMP) and protein kinase G (PKG) concentrations, together with down-regulation of DA receptor D4 mRNA and up-regulation of cyclic adenosine monophosphate (cAMP), protein kinase A (PKA), diacylglycerol (DAG) and protein kinase C (PKC) concentrations suggested an activation of complicated intracellular signaling pathway. The expression of cyclic AMP response element-binding protein (CREB), FXYD2 and 14-3-3 protein mRNA was significantly increased by PKA regulation. The increase in Na+/K+-ATPase (NKA) activity and the stabilization of V-type H+-ATPase (V-ATPase) activity are accompanied by an up-regulation of K+-channel, Na+/K+/2Cl− cotransporter (NKCC), Rh protein and vesicle associated membrane protein (VAMP) mRNA, resulting in an increase in hemolymph osmolality and a decrease in hemolymph ammonia concentration. These results suggest that DA stimulates the secretion of CHH and inhibits the release of cortisol, which activates intracellular signaling factors to facilitate ion and ammonia transport across the gills, and may not affect intracellular acidification.