Rapid modulation of Na+/K+-ATPase activity in osmoregulatory tissues of a salmonid fish

2001 ◽  
Vol 204 (4) ◽  
pp. 701-709 ◽  
Author(s):  
C.K. Tipsmark ◽  
S.S. Madsen
Keyword(s):  
Cyclic Amp ◽  
Atpase Activity ◽  
Salmo Trutta ◽  
Kidney Tissue ◽  
Gill Tissue ◽  
Phosphatase Inhibitors ◽  
Protein Phosphatase Inhibitors ◽  
Brown Trout Salmo Trutta ◽  
Series Of Experiments ◽  
Rapid Modulation

The effects of cyclic AMP on Na+/K+-ATPase activity were studied in the gill and kidney of the euryhaline brown trout Salmo trutta using two different experimental approaches. In the first series of experiments, in situ Na+/K+-ATPase activity was analyzed by measuring the ouabain-sensitive uptake of non-radioactive rubidium (Rb+) into gill cells and blocks of gill and kidney tissue. Rubidium uptake was linear for at least 30 min and was significantly inhibited by 1 mmol × l(−1) ouabain. Several agents presumed to increase the intracellular cyclic AMP concentration inhibited ouabain-sensitive Rb+ uptake in both gill (0.5 and 2 mmol × l(−1) dibutyryl-cyclic AMP, 1 mmol × l(−1) theophylline, 10 micromol × l(−1) forskolin and 10 micromol × l(−1)isoproterenol) and kidney (10 micromol × l(−1) forskolin) tissue from freshwater-acclimated fish. In a separate series of experiments, ATP hydrolase activity was assayed in a permeabilised gill membrane preparation after incubation of tissue blocks with 10 micromol × l(−1)forskolin. Forskolin elevated gill cyclic AMP levels 40-fold, inhibited maximal enzymatic Na+/K+-ATPase activity (Vmax) in gill tissue from both freshwater- and seawater-acclimated fish and reduced the apparent K+ affinity in the gills of seawater-acclimated fish, demonstrating that the effects are mediated through modifications of the enzyme itself. The protein phosphatase inhibitors okadaic acid and cyclosporin A did not affect forskolin-induced inhibition of Na+/K+-ATPase activity, indicating that forskolin-mediated modulation was stable for the duration of assay. We suggest that cyclic-AMP-mediated phosphorylation through protein kinases may underlie the rapid modulation of Na+/K+-ATPase activity in the osmoregulatory tissues of euryhaline teleosts.

scholarly journals Endocrine control of Na+,K+-ATPase and chloride cell development in brown trout (Salmo trutta): interaction of insulin-like growth factor-I with prolactin and growth hormone

1999 ◽  
Vol 162 (1) ◽  
pp. 127-135 ◽  
Author(s):  
M Seidelin ◽  
SS Madsen
Keyword(s):  
Growth Hormone ◽  
Growth Factor ◽  
Atpase Activity ◽  
Cell Density ◽  
Salmo Trutta ◽  
Mrna Level ◽  
Plasma Osmolality ◽  
Factor I ◽  
Igf I ◽  
Brown Trout Salmo Trutta

A 2-factorial (3x3) injection experiment was used to investigate the effect and interaction between different hormones on the initial phase of seawater (SW) acclimation in brown trout (Salmo trutta). Each fish was given 4 injections on alternate days in freshwater (FW). Factor 1 was either saline, 2 micrograms ovine prolactin (oPRL)/g, or 2 micrograms ovine growth hormone (oGH)/g. Factor 2 was either 0, 0. 01, or 0.1 mirograms recombinant human insulin-like growth factor-I (rhIGF-I)/g. In each of the 9 treatment groups, half of the fish were subjected to a 48-h SW-challenge test, and the remaining fish were sham-transferred to FW one day after the last injection. Hypo-osmoregulatory performance was increased by GH and impaired by PRL treatment as judged by changes in plasma osmolality, [Na+], [Cl-], total [Mg] and muscle water content (MWC) after SW transfer. IGF-I reduced plasma osmolality after transfer to SW but had no effect on plasma total [Mg] or MWC. The effects of the two factors on plasma osmolality, [Na+], [Cl-], and MWC were additive. In sham-transferred fish, GH and IGF-I, alone and in combination, stimulated Na+,K+-ATPase alpha-subunit mRNA (alpha-mRNA) content in the gill. This was paralleled by an overall increase in gill Na+, K+-ATPase activity in fish treated with 0.01 micrograms IGF-I/g. Simultaneous administration of PRL completely inhibited the increase in gill alpha-mRNA observed in the IGF-I-injected groups. Combination of GH and IGF-I did not further affect the alpha-mRNA level relative to the single hormone-injected groups. There was an overall decrease in Na+,K+-ATPase activity in pyloric caeca and middle intestine by the low dose and both doses of IGF-I respectively. No effect was observed in the posterior intestine. PRL and GH treatments did not affect enzyme activity in any intestinal segment. Both doses of IGF-I increased Na+,K+-ATPase-immunoreactive (NKIR) cell density in gill primary filaments. PRL and GH had no effect on primary filament NKIR cell density. GH and both doses of IGF-I reduced secondary lamellar NKIR cell density, whereas PRL had no effect. The main conclusion is that IGF-I and GH induce an overall redistribution of NKIR cells away from the secondary lamella onto the primary filament of FWacclimated trout. This is associated with an overall increased alpha-mRNA level in the gill, which may reflect an increased expression within individual NKIR cells in the primary filament. PRL completely abolished the IGF-I stimulation of alpha-mRNA levels, suggesting a desensitisation of the gill tissue to IGF-I, which may explain the overall anti-SW adaptive effect of PRL.

Expression of Na(+)-K(+)-ATPase in the brown trout, Salmo trutta: in vivo modulation by hormones and seawater

1995 ◽  
Vol 269 (6) ◽  
pp. R1339-R1345 ◽  
Author(s):  
S. S. Madsen ◽  
M. K. Jensen ◽  
J. Nhr ◽  
K. Kristiansen
Keyword(s):  
Atpase Activity ◽  
Salmo Trutta ◽  
Mrna Level ◽  
Gill Tissue ◽  
Northern Blotting ◽  
Bovine Insulin ◽  
Alpha Subunit ◽  
Control Fish ◽  
Subunit Mrna

Expression of the Na(+)-K(+)-ATPase alpha-subunit was investigated in the gill and trunk kidney of Salmo trutta. Groups of freshwater (FW) fish were treated with various hormones [cortisol: 3 x 4.0 micrograms/g; recombinant salmon growth hormone (rsGH): 3 x 0.25 micrograms/g; salmon prolactin (sPRL): 3 x 0.25 micrograms/g; recombinant bovine insulin-like growth factor-I (rbIGF-I): 2 x 0.01 micrograms/g; or 2 x 0.1 micrograms/g] or transferred to 25 parts per thousand seawater (SW) and sampled after 1, 2, 3, and 50 days. Total RNA was analyzed by Northern blotting using Xenopus laevis Na(+)-K(+)-ATPase alpha-subunit cDNA as probe. The probe detected a 3.8-kb transcript. Relative to untreated FW control fish, the abundance of alpha-subunit Na(+)-K(+)-ATPase mRNA in gill tissue increased 1.7-to 2.5-fold after treatment with cortisol, rsGH, and rbIGF-I and after transfer to SW. Na(+)-K(+)-ATPase enzyme activity was also significantly stimulated in these groups, except at 0.01 micrograms/g rbIGF-I. sPRL was without effect. In the kidney, alpha-subunit mRNA level and Na(+)-K(+)-ATPase activity were unaffected by hormone treatment and SW transfer. The results indicate that an increased abundance of alpha-subunit mRNA is part of the molecular mechanism behind the increased gill Na(+)-K(+)-ATPase activity induced by SW transfer, cortisol, GH, and IGF-I.

Relationship between gill Na+,K+-ATPase activity and downstream movement in domesticated and first-generation offspring of wild anadromous brown trout (Salmo trutta)

2000 ◽  
Vol 57 (10) ◽  
pp. 2086-2095 ◽  
Author(s):  
Kim Aarestrup ◽  
Christian Nielsen ◽  
Steffen S Madsen
Keyword(s):  
Atpase Activity ◽  
Brown Trout ◽  
Salmo Trutta ◽  
First Generation ◽  
Water Discharge ◽  
Daily Basis ◽  
Brown Trout Salmo Trutta ◽  
The Relationship ◽  
Downstream Movement ◽  
Generation Offspring

The relationship between smolt status and downstream movement following release was investigated in two stocks of hatchery-reared anadromous brown trout (Salmo trutta). Yearlings from a domesticated stock (DS) and first-generation offspring (F1) of wild anadromous trout were held under identical conditions from August 1997 until the following spring, where they developed smolt characteristics as judged from increasing gill Na+,K+-ATPase activity. Presmolts (low Na+,K+-ATPase activity), smolts (high Na+,K+-ATPase activity), and desmolts (regressed Na+,K+-ATPase activity) were released on three occasions into the River Salten. Using both dye-marked and radiotagged fish, downstream movement was monitored by either trapping 3 km downstream (dye-marked fish) or radiotracking on a daily basis. The experiments showed a positive correlation between smolt status (gill Na+,K+-ATPase activity) and downstream movement. Gill Na+,K+-ATPase activity may therefore be used as an indicator of migratory readiness in brown trout. F1 and DS trout had the highest migration frequency when released as presmolts and smolts, respectively. Despite smaller size, F1 trout had similar or better survival than DS trout after release. Our data suggest that initiation of downstream movement is influenced by an interaction between the previous physiological development of the fish and a discrete level of water discharge or water temperature.

Sign in / Sign up

Export Citation Format

Share Document