title: Implication of the mineralocorticoid axis in rainbow trout osmoregulation during salinity acclimation.
abstract: Cortisol and glucocorticoid receptors (GRs) play an important role in fish osmoregulation, whereas the involvement of the mineralocorticoid receptor (MR) and its putative ligand 11-deoxycorticosterone (DOC) is poorly investigated. In this study, we assessed the implication of DOC and MR in rainbow trout (Oncorhynchus mykiss) osmoregulation during hypo- and hypersaline acclimation in parallel with the cortisol-GR system. A RIA for DOC was developed to measure plasma DOC levels, and a MR-specific antibody was developed to localize MR protein in the gill, intestine, and kidney. This is the first study to report DOC plasma levels during salinity change and MR localization in fish osmoregulatory tissue. Corticosteroid receptor mRNA abundance was investigated in osmoregulatory tissue during salinity acclimation, and the effect of cortisol and DOC on ionic transporters gene expression was assayed using an in vitro gill incubation method. Differential tissue-, salinity-, and time-dependent changes in MR mRNA levels during both hyper- and hyposaline acclimations and the ubiquitous localization of MR in osmoregulatory tissue suggest a role for the MR in osmoregulation. Presumably, DOC does not act as ligand for MR in osmoregulation because there were no changes in plasma DOC levels during either freshwater-seawater (FW-SW) or SW-FW acclimation or any effect of DOC on gill ionic transporter mRNA levels in the gill. Taken together, these results suggest a role for MR, but not for DOC, in osmoregulation and confirm the importance of cortisol as a major endocrine regulator of trout osmoregulation.
authors.affiliation: INRA-SCRIBE, IFR 140, Campus de Beaulieu, 35042 Rennes cedex, France.
authors.forename: Pia
authors.initials: P
authors.lastname: Kiilerich
authors.forename: Sylvain
authors.initials: S
authors.lastname: Milla
authors.forename: Armin
authors.initials: A
authors.lastname: Sturm
authors.forename: Claudiane
authors.initials: C
authors.lastname: Valotaire
authors.forename: Sylvie
authors.initials: S
authors.lastname: Chevolleau
authors.forename: Franck
authors.initials: F
authors.lastname: Giton
authors.forename: Xavier
authors.initials: X
authors.lastname: Terrien
authors.forename: Jean
authors.initials: J
authors.lastname: Fiet
authors.forename: Alexis
authors.initials: A
authors.lastname: Fostier
authors.forename: Laurent
authors.initials: L
authors.lastname: Debrauwer
authors.forename: Patrick
authors.initials: P
authors.lastname: Prunet
mesh_terms: D000064:Acclimatization; D000818:Animals; D000918:Antibody Specificity; D003900:Desoxycorticosterone / Q000097:blood*; D005880:Gills / Q000378:metabolism; D006854:Hydrocortisone / Q000097:blood; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000097:blood*; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D018161:Receptors, Mineralocorticoid / Q000276:immunology / Q000378:metabolism*; D054712:Salinity; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014882:Water-Electrolyte Balance
chemical_list: D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D003900:Desoxycorticosterone; D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone