title: Differential regulation of cystic fibrosis transmembrane conductance regulator and Na+,K+ -ATPase in gills of striped bass, Morone saxatilis: effect of salinity and hormones.
abstract: Effects of salinity and hormones on cystic fibrosis transmembrane conductance regulator (CFTR) and alpha-subunit Na(+),K(+) -ATPase (alpha-NKA) mRNA (analysed by semi-quantitative PCR) and protein expression (analysed by western blotting and immunocytochemistry) were investigated in gills of striped bass. Freshwater (FW) to seawater (SW) transfer induced a disturbance in serum [Na(+)]. Gill CFTR protein, mRNA level and Na(+),K(+) -ATPase activity were unaffected by SW transfer, whereas alpha-NKA mRNA increased after transfer. CFTR immunoreactivity was observed in large cells in FW and SW gill filaments at equal intensity. Cortisol decreased serum [Na(+)] in FW fish, but had no effect on gill Na(+),K(+) -ATPase activity, alpha-NKA and CFTR mRNA levels. Incubation of gill tissue with cortisol (24 h, >0.01 micro g/ml) and epidermal growth factor (EGF 10 micro g/ml) decreased CFTR mRNA levels relative to pre-incubation and control levels. CFTR expression was unaffected by IGF-I (10 micro g/ml). alpha-NKA mRNA levels decreased by 50% after 24 h control incubation; it was slightly stimulated by cortisol and unaffected by IGF-I and EGF. In isolated gill cells, phosphorylation of extracellular-regulated kinase (ERK) 1/2 was stimulated by EGF but not affected by IGF-I. This study is the first to report a branchial EGF response and to demonstrate a functional ERK 1/2 pathway in the teleost gill. In conclusion, CFTR and Na(+),K(+) -ATPase are differentially regulated by salinity and hormones in gills of striped bass, despite the putative involvement of both in salt excretion.
authors.affiliation: Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark. steffen@biology.sdu.dk
authors.forename: Steffen Søndergaard
authors.initials: SS
authors.lastname: Madsen
authors.forename: Lars Nørholm
authors.initials: LN
authors.lastname: Jensen
authors.forename: Christian Kølbaek
authors.initials: CK
authors.lastname: Tipsmark
authors.forename: Pia
authors.initials: P
authors.lastname: Kiilerich
authors.forename: Russell John
authors.initials: RJ
authors.lastname: Borski
mesh_terms: D000818:Animals; D001483:Base Sequence; D001492:Bass / Q000378:metabolism / Q000502:physiology*; D015153:Blotting, Western / Q000379:methods; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005618:Fresh Water; D005880:Gills / Q000378:metabolism*; D006854:Hydrocortisone / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D021122:Protein Subunits / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012623:Seawater; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D014882:Water-Electrolyte Balance
chemical_list: D017931:DNA Primers; D021122:Protein Subunits; D012333:RNA, Messenger; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D012964:Sodium; D020929:Mitogen-Activated Protein Kinase Kinases; D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone