Progressive transfer to seawater enhances intestinal and branchial Na+-K+ATPase activity in non-anadromous rainbow trout (original) (raw)
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Journal of Animal and Plant Sciences
In this study, rainbow trout (Oncorhynchus mykiss) (162.7 ± 3.03 g) and brown trout (Salmo trutta forma fario) (160.9 ± 2.94 g) were transferred to full-strength seawater (36.5 g.l-1) for directly and gradually (21 days), then changes in gill Na+-K+-ATPase activity and size of chloride cells associated with environmental salinity were investigated and also survival of trouts were evaluated in seawater. All fish died when brown trouts were transferred into seawater directly but rainbow trouts survived 50 – 58.3 %. However, significant difference was recorded between brown and rainbow trouts in terms of survival rates by gradual acclimation. Survival of brown trout and rainbow trout that were transferred in seawater gradually, was 66.7 – 75 % and 83.3 – 91.7 %, respectively (p < 0.05). Gill chloride cell sizes in both species increased at 36.5 g.l-1 salinity. The lowest sectional area of chloride cells was determined at the point of death in brown trouts which were transferred dire...
Physiological and Biochemical Zoology, 2000
Changes in expression of Na, K-ATPase (NKA) and morphometry of mitochondrion-rich (MR) cells in gills of tilapia were investigated on a 96-hr time course following transfer from seawater (SW) to fresh water (FW). A transient decline in plasma osmolality and Na þ , Cl À concentrations occurred from 3 hrs onward. Gills responded to FW transfer by decreasing NKA activity as early as 3 hrs from transfer. This response was followed by a significant decrease in the NKA isoform a1-mRNA abundance, which was detected by real-time PCR at 6 hrs post transfer. Next, a decrease of a1-protein amounts were observed from 6 hrs until 24 hrs post transfer. Additionally, during the time course of FW transfer, modifications in number and size of subtypes of gill MR cells were observed although no significant difference was found in densities of all subtypes of MR cells. These modifications were found as early as 3 hrs, evident at 6 hrs (exhibition of 3 subtypes of MR cells), and mostly completed by 24 hrs post transfer. Such rapid responses (in 3 hrs) as concurrent changes in branchial NKA expression and modifications of MR cell subtypes are thought to improve the osmoregulatory capacity of tilapia in acclimation from hypertonic SW to hypotonic FW.
… and Physiology Part B: …, 1992
Rainbow trout adapated to freshwater (FW) and brackish water (BW) exhibit an ouabaininsensitive gill Na+-ATPase activity that roughly reproduces the enzyme features previously described in osmoregulatory organs from euryhaline teleosts. 2. The Na+-ATPase activity is higher in FW than in BW, at odds with the previously characterized coexistent (Na + + K+)-ATPase. 3. The enzyme response to the assay pH, MgATP and Na + concentrations is quite similar in the two habitats. The Na+-ATPase is maximally activated at pH 5.2, 6 mM MgATP and 40-60 mM Na +, in FW and BW, respectively, with Michaelian activation kinetics by MgATP and Na + in both habitats. 4. The possible role of the Na+-ATPase in the active salt uptake from the environment is discussed and related to teleost osmoregulation under different salinity conditions.
Aquaculture, 1987
Salman, N.A. and Eddy, F.B., 1987. Response of chloride cell numbers and gill Na+/K+ ATPase activity of freshwater rainbow trout (Salmo gairdneri Richardson) to salt feeding. Aquaculture, 61: 41-48. Dietary NaCI up to the level of 12% was fed to freshwater rainbow trout (40-120 g]. The experiment was conducted between January and June 1984. Similar to the response to seawater transfer, fish fed the high level of salt showed an increase in numbers of chloride cells and gill Na */K +-ATPase activity. The proportion of chloride cells to the total ceil population increased from 8% in the normally fed fish to 10.5% in fish fed 12% salt. A positive linear kelationship was found between the increased level of salt in the diet and both chloride cell numbers and gill Na+/K+-ATPase activity. Structure of the gill surface showed larger chloride cells occurring more frequently at the base of the secondary lamella in fish fed the salty diets.
Scientific Reports
Na+/K+-ATPases (NKA) in the basolateral membrane of the intestinal enterocytes create a Na+-gradient that drives both ion-coupled fluid uptake and nutrient transport. Being dependent on the same gradient as well as on the environmental salinity, these processes have the potential to affect each other. In salmonids, L-lysine absorption has been shown to be higher in freshwater (FW) than in seawater (SW) acclimated fish. Using electrophysiology (Ussing chamber technique), the aim was to explore if the decrease in L-lysine transport was due to allocation of the Na+-gradient towards ion-driven fluid uptake in SW, at the cost of amino acid transport. Intestinal NKA activity was higher in SW compared to FW fish. Exposure to ouabain, an inhibitor of NKA, decreased L-lysine transport. However, exposure to bumetanide and hydrochlorothiazide, inhibitors of Na+, K+, 2Cl−-co-transporter (NKCC) and Na+, Cl−-co-transporter (NCC) respectively, did not affect the rate of intestinal L-lysine transpo...
Response of rainbow trout gill (Na++K+)-ATPase and chloride cells to T3 and NaCl administration
Fish Physiology and Biochemistry, 1996
With the aim of comparing the effects of oral T 3 and NaC1 administration on trout hypoosmoregulatory mechanisms, three groups of rainbow trout (Oncorhynchus mykiss Walbaum) held in freshwater (FW) were fed a basal diet (C), the same diet containing 8.83 ppm of 3,5,3'-triiodo-L-thyronine (T3) (T) or 10% (w/w) NaC1 (N) respectively for 30 d. They were then transferred to brackish water (BW) for 22 d and fed on diet C. Gill (Na++K+)-ATPase activity and its dependence on ATP, Na + and pH, number of gill chloride cells (CC), serum T 3 level as well as fish growth, condition factor (K) and mortality were evaluated. During the FW phase, as compared to C trout, T trout showed a two fold higher serum T 3 level, had unchanged gill (Na~+K+)-ATPase activity and increased CC number, whereas N trout showed higher gill (Na~+K+) -ATPase activity and CC number. At the end of the experiment the enzyme activity was in the order T > N > C groups and all groups showed similar CC number. Both treatments changed the enzyme activation kinetics by ATP and Na +. A transient increase in K value occurred in N group during the period of salt administration. In BW, T and N groups had higher and lower survival than C group respectively. Other parameters were unaffected by the treatments. This trial suggests that T 3 administration promotes the development of hypoosmoregulatory mechanisms of trout but it leaves the (Na++K+)-ATPase activity unaltered till the transfer to a hyperosmotic environment.
The Journal of experimental biology, 1995
Dietary Na+ loads (0.570 mmol kg-1 fish) were almost completely absorbed within 7 h, and branchial Na+ excretion commenced within 1 h. Na+ loads of less than 1 mmol kg-1 were lost through the gills through a significant decrease in Na+ influx with unaltered Na+ efflux rate (compared with Na+ fluxes in unfed fish). At higher salt loads (>18 mmol kg-1), Na+ loss increased as a result of significantly higher Na+ efflux rates, with no further decrease in Na+ influx rate. Tissue Na+ concentrations were unchanged, apart from a significant increase in blood plasma Na+ concentration in fish loaded above 18 mmol kg-1. The results show that branchial Na+ fluxes may be rapidly adjusted in response to prevailing conditions, and possible control mechanisms are discussed.
Journal of Experimental Zoology, 2002
The dynamics of branchial Na+,K+,2Cl− cotransporter (NKCC) and Na+,K+-ATPase (NKA) expression were investigated in brown trout and Atlantic salmon during salinity shifts and the parr-smolt transformation, respectively. In the brown trout, Western blotting revealed that NKCC and NKA abundance increased gradually and in parallel (30- and ten-fold, respectively) after transfer to seawater (SW). The NKA hydrolytic activity increased ten-fold after SW-transfer. Following back-transfer to fresh water (FW), the levels of both proteins and NKA activity decreased. The NKCC immunostaining in the gill of SW-acclimated trout was strong, and mainly localized in large cells in the filament and around the bases of the lamellae. In FW-acclimated trout, immunostaining was less intense and more diffuse. Partial cDNAs of the secretory NKCC1 isoform were cloned and sequenced from both brown trout and Atlantic salmon gills. Two differently sized transcripts were detected by Northern blotting in the gill but not in other osmoregulatory tissues (kidney, pyloric caeca, intestine). The abundance in the gill of these transcripts and of the associated NKCC protein increased four- and 30-fold, respectively, during parr-smolt transformation. The abundance of NKA α-subunit protein also increased in the gill during parr-smolt transformation though to a lesser extent than enzymatic activity (2.5- and eight-fold, respectively). In separate series of in vitro experiments, cortisol directly stimulated the expression of NKCC mRNA in gill tissue of both salmonids. The study demonstrates the coordinated regulation of NKCC and NKA proteins in the gill during salinity shifts and parr-smolt transformation of salmonids. © 2002 Wiley-Liss, Inc.