Effects of Growth Hormone and Cortisol on Na+–K+–2Cl− Cotransporter Localization and Abundance in the Gills of Atlantic Salmon

Abstract

The hormones responsible for the regulation of the teleostean gill Na ؉ -K ؉ -2Cl ؊ cotransporter have not been elucidated. With Western blotting and immunocytochemistry, Na ؉ -K ؉ -2Cl ؊ cotransporter abundance and localization were examined in the gills of Atlantic salmon (Salmo salar) following 2-week treatment with growth hormone (GH; 5.0 g ⅐ g ؊1 ), cortisol (50 g ⅐ g ؊1 ), and both hormones in combination (GH؉cortisol). GH and cortisol treatments increased gill Na ؉ -K ؉ -2Cl ؊ cotransporter abundance over levels seen in controls, and both hormones together (GH؉cortisol) produced a greater effect than either hormone alone. Gill Na ؉ ,K ؉ -ATPase activity was also elevated by all three hormone treatments. Compared to controls, Na ؉ -K ؉ -2Cl ؊ cotransporter immunoreactive chloride cells on the primary filament were greater in number and size following all three treatments. Although the number of immunoreactive chloride cells on the secondary lamellae did not differ among the treatment groups, GH؉cortisol increased their size. These data indicate that GH and cortisol increase gill Na ؉ -K ؉ -2Cl ؊ cotransporter abundance through chloride cell proliferation and differentiation in the gills of Atlantic salmon and are likely the hormones responsible for Na ؉ -K ؉ -2Cl ؊ cotransporter regulation during smolting and seawater acclimation.

Cortisol regulation of ion transporter mRNA in Atlantic salmon gill and the effect of salinity on the signaling pathway

“…Previously, cortisol stimulated NKCC mRNA in FW gill in vitro (Tipsmark et al 2002) and NKCC protein level in vivo (Pelis & McCormick 2001). A reason for the disparity in response to cortisol in the FW gill may be found in seasonal variation of sensitivity of the gill, since post-smolt salmon were used in this study whereas Tipsmark et al (2002) Scott et al (2005), where neither RU486 nor spironolactone implants affected the suppression of NKCC mRNA levels in BW-to FW-transferred killifish (Scott et al 2005).…”

Effects of cortisol and salinity acclimation on Na⁺/K⁺/2Cl^–- cotransporter gene expression and Na⁺, K⁺-ATPase activity in the gill of Persian sturgeon, <i>Acipenser persicus</i>, fry

“…Cortisol is the first and most important hormone that stimulates Na + , K + -ATPase activity (Pickford et al, 1970). An increase in gill Na + , K + -ATPase activity in response to cortisol treatment was previously reported in different species (Oncorhynchus mykiss [Shrimpton and McCormick, 1999]; Salmo trutta [Seidelin et al, 1999]; Anguilla japonica [Wong and Chan, 2001]; Salmo salar [Pelis and McCormick, 2001]; Sparus aurata [Mancera et al, 2002]). Some other observations also showed that exogenous cortisol can stimulate Na + , K + -ATPase activity and mitochondrion content of the ionocytes and ionocyte distribution in the gill epithelium of freshwater and seawater-adapted fishes (Laurent and Perry, 1990;Madsen, 1990b;McCormick, 1990;Seidelin et al, 1999).…”

“…Na + is transported through a paracellular pathway down its electrical gradient (McCormick, 1990). This mechanism showed that every change in Na + , K + -ATPase activity and abundance can be affected by NKCC cotransporter (Pelis and McCormick, 2001). Increasing NKCC gene expression after acclimation to salinity was previously reported in Anguilla japonica (Tse and Wong, 2006), Dicentrarchus labrax (acclimated to 36 ppt salinity) (Lorin-Nebel et al, 2006), Anguilla Anguilla and Fundulus heteroclitus (acclimated to 35 ppt salinity) (Scott et al, 2004;Scott and Schulte, 2005).…”

“…We propose that in the salinity-acclimated group of Acipenser persicus no significant changes in Na + , K + -ATPase activity can be compensated by increasing NKCC gene expression and that this cotransporter excreted the additional Na + , K + and Clions to the external medium. Pelis and McCormick (2001), and Kiilerich et al (2007) reported that cortisol treatment increases the NKCC abundance in gill of Atlantic salmon, Salmo salar. Hirose et al (2003), in a review paper, also stated that cortisol treatment can increase NKCC gene expression and protein in gills of many fish species.…”

“…Whereas prolactin has been established as an important hormone for the maintenance of ionic homeostasis in freshwater, growth hormone (GH) and cortisol are recognised as the major seawater-adapting hormones (Madsen, 1990a and1990b;McCormick, 1995;Kiilerich et al, 2007). Many studies have shown that changes in salinity and hormones such as cortisol, growth hormone (GH) and prolactin (PRL) can stimulate expression and activity of different ion and electrolyte transporters in the ionocytes, such as NKA and NKCC (Pelis and McCormick, 2001;Mancera et al, 2002;Singer et al, 2003;Lin et al, 2004;Tse et al, 2006;).…”