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- Cortisol and parathyroid hormone-related peptide are reciprocally modulated by negative feedbackPublication . Guerreiro, P. M.; Rotllant, J.; Fuentes, J.; Power, Deborah; Canario, Adelino V. M.In previous in vitro studies, we have shown that the N-terminal region of parathyroid hormone-related protein (PTHrP) can stimulate cortisol production in sea bream, Sparus auratus, interrenal tissue, possibly through a paracrine action. In the current study, the systemic interaction between cortisol and PTHrP was studied in vivo. Sustained elevated blood cortisol levels, induced either by cortisol injection or conWnement stress, suppressed circulating PTHrP 6 and 24-fold,respectively, by comparison to control Wsh.reduced cortisol levels, prevented the decrease of plasma PTHrP observed in conWned Wsh and raised plasma PTHrPrespectively, by comparison to control fish.
- Expression of pituitary prolactin, growth hormone and somatolactin is modified in response to different stressors (salinity, crowding and food-deprivation) in gilthead sea bream Sparus auratusPublication . Laiz-Carrión, R.; Fuentes, J.; Redruello, Begoña; Guzmán, José M.; Río, María P. Martín del; Power, Deborah; Mancera, J. M.Prolactin (PRL), growth hormone (GH) and somatolactin (SL) expression was studied in gilthead sea bream (Sparus auratus) in response to several different stressors (salinity, food deprivation or stocking density). In the first experiment, specimens were acclimated during 100 days at three different environmental salinities: low salinity water (LSW, 6 ppt), brackish water (BW, 12 ppt) and seawater (SW, 38 ppt). Osmoregulatory parameters corresponded to those previously reported for this species under similar osmotic conditions. Pituitary PRL expression increased with decreasing environmental salinity, and was significantly different between SW- and LSW-acclimated fish. Pituitary GH expression was similar between SW- and BW-acclimated fish but decreased in LSW-acclimated specimens. Pituitary SL expression had a ‘‘U-shaped” relationship to environmental salinity with the lowest expression in BW-acclimated fish. In a second experiment SW-acclimated specimens were randomly assigned to one of four treatments and maintained for 14 days: (1) fed fish under low density (LD, 4 kg m!3); (2) fed fish under high density (HD, 70 kg m!3); (3) food deprived fish under LD; and (4) food deprived fish under HD. Plasma glucose and cortisol levels corresponded to those previously reported in S. auratus under similar experimental conditions. Pituitary PRL and SL expression increased in fish maintained under HD and decreased in food deprived fish. In conclusion, an effect of environmental salinity on pituitary PRL and GH expression has been demonstrated. In addition, crowding stress seems to interact with food deprivation in S. auratus and this is reflected by changes in pituitary PRL, GH and SL expression levels.
- Isolation of a novel aquaglyceroporin from a marine teleost (Sparus auratus) Function and tissue distributionPublication . Santos, C. R. A.; Estêvão, Dulce; Fuentes, J.; Cardoso, João CR; Fabra, Mercedes; Passos, A. L.; Detmers, F. J.; Deen, P. M. T.; Cerda, J.; Power, DeborahThe aquaporins (formerly called the major intrinsic protein family) are transmembrane channel proteins. The family includes the CHIP group, which are functionally characterised as water channels and the GLP group, which are specialised for glycerol transport. The present study reports the identification and characterisation of a novel GLP family member in a teleost fish, the sea bream Sparus auratus. A sea bream aquaporin (sbAQP) cDNA of 1047·bp and encoding a protein of 298·amino acids was isolated from a kidney cDNA library. Functional characterization of the sbAQP using a Xenopus oocyte assay revealed that the isolated cDNA stimulated osmotic water permeability in a mercury-sensitive manner and also stimulated urea and glycerol uptake. Northern blotting demonstrated that sbAQP was expressed at high levels in the posterior region of the gut, where two transcripts were identified (1.6·kb and 2·kb), and in kidney, where a single transcript was present (2·kb). In situ hybridisation studies with a sbAQP riboprobe revealed its presence in the lamina propria and smooth muscle layer of the posterior region of the gut and in epithelial cells of some kidney tubules. sbAQP was also present in putative chloride cells of the gill. Phylogenetic analysis of sbAQP, including putative GLP genes from Fugu rubripes, revealed that it did not group with any of the previously isolated vertebrate GLPs and instead formed a separate group, suggesting that it may be a novel GLP member.