Expression profiles of genes encoding arginine vasotocin and isotocin receptors and the leucyl-cystinyl aminopeptidase (LNPEP) nonapeptide degradation enzyme in blue tilapia (Oreochromis aureus) during high salinity acclimation

ABSTRACT The nonapeptide hormone arginine vasotocin (VT) regulates osmotic balance in fishes by modulating ion and water transport. While VT’s osmoregulatory effects arise in part via changes in VT secretion, it remains uncertain which nonapeptide receptors mediate these effects, or whether adjustments in VT degradation also contribute. This study characterized gene transcript profiles for all known teleost nonapeptide receptors and for the VT and isotocin (IT) degradation enzyme leucyl-cystinyl aminopeptidase (lnpep) in the gill, kidney, and intestine – as well as transcriptional profiles for proVT and proIT mRNAs in hypothalamus and pituitary – of blue tilapia (Oreochromis aureus) during hyperosmotic challenge. Results presented here suggest that VT’s actions during salinity acclimation may be mediated by V1a-type receptor V1a2 in gill and intestine but multiple V2-type receptors in kidney, and provide evidence that lnpep expression is modulated concurrent with osmoregulation, possibly to alter local availability of nonapeptides as osmolality returns to homeostatic set points.