Enhanced Hypo-Osmoregulation Induced by Warm-Acclimation in Antarctic Fish is Mediated by Increased Gill and Kidney Na+ /K+ - ATPase Activities (original) (raw)
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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.
Journal of Comparative Physiology B, 2004
This study examined the osmoregulatory status of the euryhaline elasmobranch Carcharhinus leucas acclimated to freshwater (FW) and seawater (SW). Juvenile C. leucas captured in FW (3 mOsm l À1 kg À1) were acclimated to SW (980-1,000 mOsm l À1 kg À1) over 16 days. A FW group was maintained in captivity over a similar time period. In FW, bull sharks were hyper-osmotic regulators, having a plasma osmolarity of 595 mOsm l À1 kg À1. In SW, bull sharks had significantly higher plasma osmolarities (940 mOsm l À1 kg À1) than FW-acclimated animals and were slightly hypoosmotic to the environment. Plasma Na + , Cl À , K + , Mg 2+ , Ca 2+ , urea and trimethylamine oxide (TMAO) concentrations were all significantly higher in bull sharks acclimated to SW, with urea and TMAO showing the greatest increase. Gill, rectal gland, kidney and intestinal tissue were taken from animals acclimated to FW and SW and analysed for maximal Na + /K +-ATPase activity. Na + /K +-ATPase activity in the gills and intestine was less than 1 mmol Pi mg À1 protein h À1 and there was no difference in activity between FW-and SW-acclimated animals. In contrast Na + /K +-ATPase activity in the rectal gland and kidney were significantly higher than gill and intestine and showed significant differences between the FW-and SW-acclimated groups. In FW and SW, rectal gland Na + /K +-ATPase activity was 5.6±0.8 and 9.2±0.6 mmol Pi mg À1 protein h À1 , respectively. Na + /K +-ATPase activity in the kidney of FW and SW acclimated animals was 8.4±1.1 and 3.3±1.1 Pi mg À1 protein h À1 , respectively. Thus juvenile bull sharks have the osmoregulatory plasticity to acclimate to SW; their preference for the upper reaches of rivers where salinity is low is therefore likely to be for predator avoidance and/or increased food abundance rather than because of a physiological constraint.
Aquaculture, 1998
. Atlantic salmon Salmo salar L. smolts were maintained in freshwater past their normal time Ž . of seawater transfer early June and reared at temperatures of 6, 10, 12 and 148C until late July. Reduction in gill Na q ,K q -ATPase activity was temperature dependent, with a significant decrease at 12 and 148C towards the end of the study. The duration of the period of good smolt status, as determined by gill Na q ,K q -ATPase activity, was approximately 280-3508C at 12 and 108C, with Ž . an extended period at 148C 4508C . All groups maintained good hypo-osmoregulatory ability despite a reduction in gill Na q ,K q -ATPase activity in freshwater. Gill Na q ,K q -ATPase activity was higher in seawater challenged smolts at 12 and 148C towards the end of the study. Desmoltification in Atlantic salmon is not a synchronised process as normally observed during Ž . smolting, nor is it a parr-reversion as seen among some Pacific salmonids Oncorhynchus spp. . q 0044-8486r98r$ -see front matter q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 0 4 4 -8 4 8 6 9 8 0 0 3 5 4 -8 ( )
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2015
a b s t r a c t 6 We investigated the impact of nutritional status on the physiological, metabolic and ion-osmoregulatory 20 performance of European sea bass (Dicentrarchus labrax) when acclimated to seawater (32 ppt), brackish 21 water (20 and 10 ppt) and hyposaline water (2.5 ppt) for 2 weeks. Following acclimation to different salinities, 22 fish were either fed or fasted (unfed for 14 days). Plasma osmolality, [Na + ], [Cl − ] and muscle water content 23 were severely altered in fasted fish acclimated to 10 and 2.5 ppt in comparison to normal seawater-acclimated 24 fish, suggesting ion regulation and acid-base balance disturbance. In contrast to feed-deprived fish, fed fish 25 were able to avoid osmotic perturbation more effectively. This was accompanied by an increase in Na + /K + -26 ATPase expression and activity, transitory activation of H + -ATPase (only at 2.5 ppt) and down-regulation of 27 Na + /K + /2Cl − gene expression. Ammonia excretion rate was inhibited to a larger extent in fasted fish acclimated 28 to low salinities while fed fish were able to excrete much more efficiently. Consequently, the build-up of 29 ammonia in the plasma of fed fish was relatively lower. Energy stores, especially glycogen and lipid, dropped 30 in the fasted fish at low salinities and progression towards the anaerobic metabolic pathway became evident 31 by an increase in plasma lactate level. Overall, the results indicate no osmotic stress in both feeding treatments 32 within the salinity range of 32 to 20 ppt. However, at lower salinities (10-2.5 ppt) feed deprivation tends to 33 reduce physiological, metabolic, ion-osmoregulatory and molecular compensatory mechanisms and thus limits 34 the fish's abilities to adapt to a hypo-osmotic environment. 35
Journal of Experimental Marine Biology and Ecology, 1999
Osmoregulatory ability and Na ,K -ATPase activity in gills and epipodites were examined 21 following transfer of the lobster Homarus gammarus from sea water (SW; 1292 mOsmol l ; 38 21 ppt salinity) to dilute seawater (DSW; 68065 mOsmol l ; 20 ppt salinity). The lobster H. gammarus behaves as an osmoconformer in sea water and a poor hyperosmoregulator when 21 * Corresponding author. 0022-0981 / 99 / $ -see front matter © 1999 Elsevier Science B. V. All rights reserved. PII: S0022-0981( 98 )00152-X 2 92
Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 2007
This study aimed to examine effects of short-or long-term acclimation to brackish water or seawater on the climbing perch, Anabas testudineus, which is an aquatic air-breathing teleost living typically in freshwater. A. testudineus exhibits hypoosmotic and hypoinoic osmoregulation; the plasma osmolality, [Na 1 ] and [Cl À ] of fish acclimated to seawater were consistently lower than those of the external medium. However, during short-term (1 day) exposure to brackish water (15%) or seawater (30%), these three parameters increased significantly. There were also significant increases in tissue ammonia and urea contents, contents of certain free amino acids (FAAs) in the muscle, and rates of ammonia and urea excretion in the experimental fish. The accumulated FAAs might have a transient role in cell volume regulation. In addition, these results indicate that increases in protein degradation and amino acid catabolism had occurred, possibly providing energy for the osmoregulatory acclimation of the gills in fish exposed to salinity stress. Indeed, there was a significant increase in the branchial Na 1 /K 1 -ATPase activity in fish exposed to seawater for a prolonged period (7 days), and the plasma osmolality, [Na 1 ] and [Cl À ] and the tissue FAA contents of these fish returned to control levels. More importantly, there was a significant increase in the dependence on water-breathing in fish acclimated to seawater for 7 days. This suggests for the first time that A. testudineus could alter its bimodal breathing pattern to facilitate the functioning of branchial Na 1 /K 1 -ATPase for osmoregulatory purposes.
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...