Effects of growth hormone and cortisol on Na+-K+-2Cl(-) cotransporter localization and abundance in the gills of Atlantic salmon

The hormones responsible for the regulation of the teleostean gill Na+-K+-2 Cl(-) cotransporter have not been elucidated. With Western blotting and imm unocytochemistry, Na+-K+-2Cl(-) cotransporter abundance and localization we re examined in the gills of Atlantic salmon (Salmo salar) following 2-week treatment with growth hormone (GH; 5.0 mug . g(-1)), cortisol (50 mug . g(- 1)), and both hormones in combination (GH+cortisol). GH and cortisol treatm ents increased gill Na+-K+-2Cl(-) cotransporter abundance over levels seen in controls, and both hormones together (GH+cortisol) produced a greater ef fect than either hormone alone. Gill Na+,K+-ATPase activity was also elevat ed by all three hormone treatments. Compared to controls, Na+-K+-2Cl(-) cot ransporter immunoreactive chloride cells on the primary filament were great er in number and size following all three treatments. Although the number o f immunoreactive chloride cells on the secondary lamellae did not differ am ong the treatment groups, GH+cortisol increased their size. These data indi cate that GH and cortisol increase gill Na+-K+-2Cl(-) cotransporter abundan ce through chloride cell proliferation and differentiation in the gills of Atlantic salmon and are likely the hormones responsible for Na+-K+-2Cl(-) c otransporter regulation during smolting and seawater acclimation. (C) 2001 Academic Press.