Differential regulation of cystic fibrosis transmembrane conductance regulator and Na+,K+ -ATPase in gills of striped bass, Morone saxatilis: effect of salinity and hormones.
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.
Madsen
Steffen Søndergaard
SS
Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark. steffen@biology.sdu.dk
Jensen
Lars Nørholm
LN
Tipsmark
Christian Kølbaek
CK
Kiilerich
Pia
P
Borski
Russell John
RJ
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
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