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1.
The capacity of cortisol, ovine growth hormone (oGH), recombinant bovine insulin-like growth factor I (rbIGF-I) and 3,3,5-triiodo-l-thyronine (T3) to increase hypoosmoregulatory capacity in the euryhaline teleost Fundulus heteroclitus was examined. Fish acclimated to brackish water (BW, 10 ppt salinity) were injected with a single dose of hormone suspended in oil and transferred to seawater (SW, 35 ppt salinity) 10 days post-injection. Fish were sampled 24 h after transfer and plasma osmolality and gill Na+, K+-ATPase activity were examined. Transfer from BW to SW induced significantly increased plasma osmolality but not gill Na+, K+-ATPase activity. Cortisol (50 g g–1 body weight) improved the ability to maintain plasma osmolality and to increase gill Na+, K+-ATPase activity. oGH (5 g g–1 body weight) also increased hypoosmoregulatory ability and gill Na+, K+-ATPase activity. A cooperation between oGH and cortisol was observed in increasing hypoosmoregulatory ability but not in increasing gill Na+, K+-ATPase activity. rbIGF-I (0.5 g g–1 body weight) alone was without effect in increasing salinity tolerance or gill Na+, K+-ATPase activity. rbIGF-I and oGH showed a positive interaction in increasing salinity tolerance, but not gill Na+, K+-ATPase activity. Treatment with T3 (5 g g–1 body weight) alone did not increase salinity tolerance or gill Na+, K+-ATPase activity, and there was no consistent significant interaction between cortisol and T3 or between GH and T3. The results confirm the classical role of cortisol as a seawater-adapting hormone and indicate an interaction between cortisol and the GH/IGF-I axis during seawater acclimation of Fundulus heteroclitus.  相似文献   

2.
The effect of cortisol on osmoregulatory parameters was studied in rainbow trout, (Salmo gairdneri), kept in freshwater (FW) and/or transferred to seawater (SW). Repeated injections of 20 μg cortisol/g fish stimulated gill and gut Na+/K+-ATPase activity and reduced plasma Na+ and Cl− levels after 2 weeks of treatment in FW-adapted fish. Cortisol doses of 0.05 and 1.0 μg/g were without effect. Repeated injections of 10 μg cortisol/g stimulated gill Na+/K+-ATPase activity and reduced plasma Na+ and Cl− levels in fish in FW, and significantly improved ion regulation after their transfer to 28SW. Higher doses of cortisol (10 and 20 μg/g) induced hyperglycemia, whereas low doses (0.05 and 1.0 μg/g were without effect or induced hypoglycemia. Plasma glucose levels decreased in cortisol-treated fish transferred to SW, whereas transient hyperglycemia was seen in the control fish.  相似文献   

3.
Several experiments were performed to investigate the physiology of seawater acclimation in the striped bass, Morone saxatilis. Transfer of fish from fresh water (FW) to seawater (SW; 31–32 ppt) induced only a minimal disturbance of osmotic homeostasis. Ambient salinity did not affect plasma thyroxine, but plasma cortisol remained elevated for 24h after SW transfer. Gill and opercular membrane chloride cell density and Na+,K+-ATPase activity were relatively high and unaffected by salinity. Average chloride cell size, however, was slightly increased (16%) in SW-acclimated fish. Gill succinate dehydrogenase activity was higher in SW-acclimated fish than in FW fish. Kidney Na+, K+-ATPase activity was slightly lower (16%) in SW fish than in FW fish. Posterior intestinal Na+,K+-ATPase activity and water transport capacity (Jv) did not change upon SW transfer, whereas middle intestinal Na+,K+-ATPase activity increased 35% after transfer and was correlated with an increase in Jv (110%). As salinity induced only minor changes in the osmoregulatory organs examined, it is proposed that the intrinsic euryhalinity of the striped bass may be related to a high degree of “preparedness” for hypoosmoregulation that is uncommon among teleosts studied to data.  相似文献   

4.
The influence of cortisol on oxygen consumption and osmoregulatory variables was examined in coastal cutthroat trout (Oncorhynchus clarki clarki) parr kept in fresh water (FW) and transferred to seawater (SW). Intraperitoneal implants containing cortisol (50 g g–1) in vegetable oil resulted in elevated plasma cortisol titres similar to those observed in fish following a 24h SW exposure. Cortisol treatment significantly increased the oxygen consumption and plasma glucose levels of trout in FW, consistent with the glucocorticoid role of cortisol. Cortisol treatment did not cause any changes in plasma ion concentrations or gill Na+,K+-ATPase activity in FW after 10 days. Cortisol-implanted fish exposed to SW for 24h showed slightly improved ion regulatory ability compare to non-implanted controls. The results of this study suggest that during SW transfer in juvenile salmonids, increases in cortisol may act as both a mineralocorticoid and a glucocorticoid, depending on the developmental state of the fish (e.g., smolt versus parr). Furthermore, the relative energetic costs of osmoregulation and that of the stress associated SW transfer cannot be discerned using whole-animal oxygen consumption rates.  相似文献   

5.
The osmoregulation capabilities of 7-month-old juvenile Chinese sturgeon (Acipenser sinensis Gray) (128.8 ± 15 g) transferred directly from fresh water (0‰, 46 mOsmol kg−1) to brackish water (10‰, 273 mOsmol kg−1) were studied over a 20-day period. Changes in serum osmolarity, chloride (Cl−), sodium (Na+), potassium (K+) and calcium (Ca2+) ion concentrations, as well as gill and spiral valve Na+,K+-ATPase activities were measured at 3, 12, 24, 72, 216 and 480 h after transfer to BW. The serum osmolarity and ion concentrations (Na+, Cl− and Ca2+) increased immediately after the transference to BW, reaching maximum at 24 h and returned to a new steady state at 216 h, while the FW control group maintained basal levels which showed lower (P < 0.05) than the BW group. Gill Na+,K+-ATPase activity of BW group exhibited an abrupt decrease in the first 3 h after transfer, but began to increase at 3 h, reaching a peak value at 24 h, and returned to a new steady state at 216 h. The differences between gill Na+,K+-ATPase activity of BW and FW fish were significant (P < 0.05) after 12 h. In contrast, Na+,K+-ATPase activity of the spiral valve showed transient increase after transference from FW to BW, and then decreased rapidly at 3 h, reaching the lowest at 24 h after transference. At 216 h after exposure to BW, Na+,K+-ATPase activities of the spiral valve increased slowly to the levels of FW control. The results of our study indicate the existence of hyposmoregulatory adaptive mechanisms in 7-month-old juvenile Chinese sturgeon which enable this fish to acclimate itself successfully to brackish water.  相似文献   

6.
The aim of this work was to determine the effects of supplemental dietary sodium chloride on salt water acclimation of tilapia Oreochromis niloticus. Fish were fed a basal diet supplemented with NaCl (8%) during three weeks in fresh water (FW) and then transferred to salt water (SW) at 15 and 20. Changes in plasma osmolality, chloride ion concentration (Cl–), plasma level of cortisol and gill Na+, K+-ATPase activity were measured at 6, 12, 24, 48, 72 and 168 h after transfer to 15SW, while the higher strength SW group (20) was only monitored up to 24 h. Morphological changes in the gill mitochondria-rich (MR) cells were examined in relation to environmental salinity. The changes associated with dietary NaCl were sporadic and of small magnitude. The plasma osmolality and Cl– increased immediately after transfer up to 12–24 h, but fish fed dietary salt (S) showed lower values than the control group (C). The S group showed higher plasma levels of cortisol than the control, which maintained its initial levels during the experiment. Gill Na+, K+-ATPase activity of the S group began to increase in the first hours after transfer, reaching maximum at 12 h and returned to basal level at 24 h, while the control group maintained basal levels. The differences between gill Na+, K+-ATPase activity of S and C fish were significant (p < 0.05) at 12 h. Transmission electron microscopy (TEM) revealed that MR cells in SW show more mitochondria and a more developed tubular system arising from the basolateral membrane. The MR cells of both groups frequently formed a multicellular complex in SW, consisting of a main MR and one or more accessory cells. Such complexes are rarely observed in FW. Some MR cells of fish fed supplemented dietary salt displayed convex apical membrane in FW.  相似文献   

7.
The response to cold of gill and kidney membrane lipid composition and microsomal (Na++K+)-ATPase, Na+-ATPase and Mg2+-ATPase activities in reared sea bass (Dicentrarchus labrax L.) was investigated. Fish acclimation was carried out according to the seasonal cycle from August to March. No cold-promoted increase in fatty acid unsaturation was shown in gill and kidney polar lipids and in total lipids of mitochondria and microsomes. In both tissues the (Na++K+)-ATPase exhibited positive compensation for cold acclimation whereas the Na+-ATPase displayed negative compensation. The Mg2+-ATPase showed no compensation in the gills and positive compensation in the kidneys. During cold acclimation the break in the Arrhenius plot of the (Na++K+)-ATPase decreased, whereas breaks of both the Na+-ATPase and the Mg2+-ATPase activities remained unchanged. The results indicate that the sea bass does not adopt membrane unsaturation as a cold-facing strategy. The cold-promoted enhancement of (Na++K+)-ATPase activity in osmoregulatory tissues may be advantageous to maintain efficient osmoregulation under thermodynamically unfavourable conditions.  相似文献   

8.
The fluid uptake rate of the posterior intestine of salmonids increases during the parr-smolt transformation. Intestinal fluid uptake in post-smolt Atlantic salmon was investigated after treatment with cortisol and growth hormone (GH), alone or together. Two replicate experiments were conducted in August 1991 and August 1992. Cortisol was emulsified in vegetable shortening and vegetable oil (1:1) and implanted into the peritoneal cavity. GH was administered as intraperitoneal injections in a saline vehicle on days 0 and 2. On days 5 and 6, plasma cortisol levels, gill Na+,K+-ATPase activity, andin vitro measurements of fluid transport rate (Jv) across the posterior intestine were measured. Implants of cortisol elevated the plasma cortisol levels within a physiological range, and resulted in elevated gill Na+,K+-ATPase activity, as expected. The fluid uptake rate across the posterior intestine was roughly doubled by cortisol treatment. GH treatment did not affect intestinal fluid transport, gill Na+,K+-ATPase activity, or plasma cortisol concentrations. The seawater-adapting increase in the rate of fluid uptake by the posterior intestine of smolting salmon is probably stimulated by elevated plasma cortisol concentrations.  相似文献   

9.
With the aim of comparing the effects of oral T3 and NaCl 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) NaCl (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 T3 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 T3 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 T3 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.  相似文献   

10.
There is increasing evidence for complex dosage effects on gene expression, enzyme activity and phenotype resulting from induced ploidy change. In this study, ocean-type chinook salmon were bred using a 2 × 2 factorial mating design to create four families and test whether triploidization resulted in changes in growth performance and smolting. Eggs were pressure shocked after fertilization to create triploid fish from a subset of each family. In June, fish were sampled for size, plasma insulin-like growth factor 1 (IGF-1), gill Na+–K+-ATPase activity, and expression of two Na+–K+-ATPase α subunits in the gill. Diploids were significantly heavier than triploids, and there were significant differences due to family. Despite a significant positive correlation between plasma IGF-1 and fish size, plasma IGF-1 did not differ between diploid and triploid smolts. Diploids also had significantly greater gill Na+–K+-ATPase enzyme activities than triploids and there was a strong family effect. Gill Na+–K+-ATPase α1b isoform expression differed significantly by family, but not ploidy, and generally families with lower Na+–K+-ATPase enzyme activity had higher α1b isoform gene expression. Na+–K+-ATPase α1a isoform expression did not differ among any of the groups. Although diploids were larger and had higher specific activities of Na+–K+-ATPase in the gills, there was no difference in gene expression or circulating hormone levels. The strong family effect, however, suggests that strain selection may be useful in improving performance of triploids for aquaculture.  相似文献   

11.
The effect of seawater acclimation and adaptation to various salinities on the energetics of gill and kidney of Atlantic salmon (Salmo salar) was examined. Smolts and non-smolts previously reared in fresh water were exposed to a rapid increase in salinity to 30 ppt. Plasma osmolarity, [Na+], [Cl–], [K+] and [Mg++] increased in both groups but were significantly lower in smolts than non-smolts. Gill Na+, K+-ATPase specific activity, initially higher in smolts, increased in both groups after 18 days in seawater. Kidney Na+, K+-ATPase specific activity was not affected by salinity in either group. Gill and kidney citrate synthase specific activity was not affected by seawater exposure in smolts but decreased in non-smolts. In a second experiment, Atlantic salmon smolts reared in fresh water were acclimated to 0, 10 or 30 ppt seawater for 3 months at a temperature of 13–14°C. Gill Na+, K+-ATPase was positively correlated with salinity, displaying 2.5- and 5-fold higher specific activity at 10 and 30 ppt, respectively, than at 0 ppt. Kidney Na+, K+-ATPase specific activity was not significantly affected by environmental salinity. Citrate synthase and cytochrome c oxidase specific activities in gill were slightly (6–13%) lower at 10 ppt than at 0 and 30 ppt, whereas kidney activities were lowest at 30 ppt. Oxygen consumption of isolated gill filaments was significantly higher when incubated in isosmotic saline and at 30 ppt than at 0 ppt, but was not affected by the prior acclimation salinity. The results indicate that although high salinity induces increased gill Na+, K+-ATPase activity, it does not induce substantial increases in metabolic capacity of gill or kidney.  相似文献   

12.
盐度胁迫对三疣梭子蟹鳃Na+/K+-ATPase酶活的影响   总被引：2，自引：2，他引：0  
江山  许强华 《水产学报》2011,35(10):1475-1480
通过钼蓝法测定三疣梭子蟹在3组实验盐度的胁迫过程中第2对和第6对鳃Na+/K+-ATPase酶活的变化,比较了3组实验盐度胁迫1 d时,鳃Na+/K+-ATPase的酶活大小。结果表明,在盐度胁迫初期,3组实验盐度下第2对和第6对鳃Na+/K+-ATPase的酶活下降;之后,各组实验盐度下第2对和第6对鳃Na+/K+-ATPase的酶活开始随胁迫时间增长而上升;最后,各组实验盐度下第2和第6对鳃Na+/K+-ATPase的酶活下降并趋于稳定。另外,胁迫1 d时,各组实验盐度下三疣梭子蟹前5对鳃Na+/K+-ATPase的酶活显著低于后3对鳃Na+/K+-ATPase的酶活。三疣梭子蟹对盐度变化的调节可分为被动应激期(酶活力下降)、主动调节期(酶活力逐渐上升)和适应期(酶活力稳定);三疣梭子蟹后3对鳃是离子转运、渗透压调节的主要部位。  相似文献   

13.
为研究盐度对珍珠龙胆石斑鱼（）渗透调节与耗氧率的影响,设计实验一,将（162.5±12.1）g珍珠龙胆石斑鱼置于不同盐度（6、12、18、24、30）下养殖10 d,测定血清渗透压及Na+、Cl-、K+离子浓度。实验结果表明,随盐度的升高血清渗透压及Na+、Cl-、K+离子浓度也随着升高,各组[Na+]：[Cl-]比值无显著差异（>0.05）;经回归分析得到血清等渗点渗透压为365.95 mOsm/kg,所对应盐度为12.75。实验二,将（26.4±2.7）g幼鱼置于不同盐度（6、12、18、24、30）下养殖30 d,测定在开始暴露后0 h、3 h、24 h、72 h鳃Na+/K+-ATPase活性及表达和第30天耗氧率,结果表明鳃Na+/K+-ATPase活性随盐度的增大呈“U”形变化;鳃Na+/K+-ATPase α1基因表达量波动较大,在72 h后随盐度增大先降低后增加,变化趋势与酶活性一致;第30天耗氧率随盐度的增加先降低后增加又降低。综上所述,珍珠龙胆石斑鱼幼鱼10 d内能够完全适应6~30盐度急性变化,耗氧率除了受离子渗透调节的影响,还可能与其生活史阶段有关。  相似文献   

14.
The osmoregulation capabilities of juvenile Siberian sturgeon exposed to three experimental osmolalities (22, 250 and 387 mOsmol kg−1) were studied over a 45-day period. Growth performance, haematological parameters, ion concentrations, gill and spiral valve Na+-K+-ATPase activities, as well as gill and spiral valve histology, were measured. At the end of the period, the plasma osmolality of fish kept in 250 and 387 mOsmol kg−1 was higher than that of fish kept in 22 mOsmol kg−1. Similar trends were observed in electrolyte concentrations. Spiral valve and gill Na+-K+-ATPase activity varied with exposure time and environmental salinity. Shortly after being transferred to hyperosmotic media, spiral valve Na+-K+-ATPase activity fell, while gill Na+-K+-ATPase activity remained constant. At the end of the experiment, gill Na+-K+-ATPase activities in fish kept in isosmotic and hyperosmotic media had increased in comparison to those of the control fish. Moreover, spiral valve Na+-K+-ATPase activities recovered and were similar to those recorded in fish kept in hyposmotic environments. Although some of the morpho-physiological mechanisms were operational in juvenile Siberian sturgeon in their adaptation to hyperosmotic media, fish cannot be considered hyperosmotic regulators as they were unable to maintain their plasma osmolality and electrolyte equilibrium in salinities higher than 250 mOsmol kg−1. This suggests that the culture of juvenile Siberian sturgeon in brackish environments is unlikely to be successful. However, our data indicate that in natural environments, juvenile Siberian sturgeon in migratory populations (Ob and Lena Rivers) would be able to migrate successfully into estuarine brackish grounds with a salinity of up to 9%. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

15.
The impact of 17-estradiol (E2) and the putative estrogenic compound, 4-nonylphenol (4-NP), on smoltification and vitellogenesis in Atlantic salmon (Salmo salar) was investigated during a 30 day period starting late April. Three groups of fresh water (FW) fish (1 year old, mixed sexes, average weight 23 g) were injected once a week with 50 µg (0.18 µmol) 17-estradiol, 3 mg (13.6 µmol) 4-nonylphenol dissolved in peanut oil, or peanut oil alone as control. Every ten days, subgroups were challenged with 28 ppt seawater (SW) for 24h, and sampled together with subgroups of FW fish. Treatment effects were examined on vitellogenic and osmoregulatory parameters. E2 and 4-NP treatment increased the total calcium and protein level in plasma and the hepatosomatic index of FW fish, both indicating an activated vitellogenesis in the liver. The presence of vitellogenin in the plasma of 4-NP- and E2-treated groups was further indicated by the appearance of a high molecular weight vitellogenin band (550 kDa) in electropherograms produced by native gel electrophoresis. This band appeared in exactly the same position in both the E2- and the 4-NP-treated groups but could not be detected in controls. During the 30 day treatment period, control fish approached the peak of smoltification, as indicated by a distinct silvery appearance, decreasing condition factor, increasing levels of gill Na+,K+-ATPase and improved hypoosmoregulatory performance in the SW-challenge test. Both E2 and 4-NP treatments significantly inhibited the progress of smoltification, as judged by a significant reduction of gill Na+,K+-ATPase activity, relative -subunit Na+,K+-ATPase mRNA expression, gill chloride cell density and a poorer hypoosmoregulatory performance of treated fish. The impaired SW-tolerance of E2- and 4-NP-treated fish was strongly correlated with a decreased gill Na+,K+-ATPase activity. Despite a difference in relative potency, the present study shows that 4-nonylphenol and 17-estradiol may have qualitatively similar inhibitory effects on smoltification and hypoosmoregulatory physiology of Atlantic salmon. Both 4-NP and E2 activated the vitellogenic system, and the study supports the hypothesis that sexual maturation and smoltification are antagonistic, developmental phenomena in salmon. It is suggested that the presence of estrogenic compounds in the environment may negatively influence smoltification and migration in wild stocks of salmon.  相似文献   

16.
Atlantic salmon (Salmo salar) exposed to either simulated natural photoperiod (SNP) or continuous light (L24) were used to examine developmental changes in the presence and absence, respectively, of the parrsmolt transformation. Plasma osmolarity and ion concentrations were unaffected by photoperiod treatment. Gill Na+, K+-ATPase specific activity increased 150% between February and June in SNP fish and was low and unchanged in L24 fish. Kidney Na+, K+-ATPase specific activity varied within similar, narrow limits in both groups. Citrate synthase of liver, gill and kidney, expressed as specific activity or activity/g total body weight (relative activity), increased 25–60% between March and June in SNP fish. With the exception of kidney relative activity, citrate synthase activity declined to initial (March) levels by August. Liver, gill and kidney cytochrome c oxidase activity of the SNP group underwent similar though less marked changes. Liver, gill and kidney citrate synthase and cytochrome c oxidase activities of the L24 group remained relatively constant between March and August, and where significant differences occurred, they were lower than those of the SNP group. These results indicate that respiratory capacities of the liver, gill and kidney increase in smolls concurrent with preparatory osmoregulatory changes, and subsequently decline. The findings are consistent with a hypothesized transient increase in catabolic activity during the parr-smolt transformation that may be due to the metabolic demands of differentiation.  相似文献   

17.
The effects of the Na+/K+ and Mg2+/Ca2+ ratios in saline groundwaters on Na+-K+-ATPase activity, survival and growth of Marsupenaeus japonicus postlarvae were investigated. The results indicate that the Na+-K+-ATPase activity, survival rate and weight gain of postlarvae were significantly affected by the Na+/K+ and Mg2+/Ca2+ ratios (P < 0.05). The Na+-K+-ATPase activity of postlarvae, in every treatment, changed corresponding to Na+/K+ and Mg2+/Ca2+ ratios, and came to a stable level after 24 h. There was a negative relation between Na+-K+-ATPase activity and Na+/K+ ratio, while there was a positive relation between Na+-K+-ATPase activity and Mg2+/Ca2+ ratio. Compared with seawater (the Na+/K+ and Mg2+/Ca2+ ratios are 27.8 and 4.64 respectively), the Na+-K+-ATPase activity of the Na+/K+ ratio 30 treatment showed no significant difference, while the Mg2+/Ca2+ ratio 4.5 treatment showed distinct difference. The survival rates and weight gain of postlarvae increased markedly when the suitable amount of K+ and Ca2+ was added to test water, and arrived at their maximum in the Na+/K+ ratio 20-30 or Mg2+/Ca2+ ratio 4.5 treatment, having no significant difference compared with normal seawater. Therefore, considering the Na+/K+, Mg2+/Ca2+ ratios and the absolute concentration of Mg2+, Ca2+ in the experimental saline groundwaters applied to Marsupenaeus japonicus farming, it should be modulated to around 30, 4.5 and 1312 mg/l, 291 mg/l, respectively.  相似文献   

18.
The effect of sulfide on K+ influx pathways was measured in red blood cells (RBCs) of sulfide-sensitive rainbow trout (Oncorhynchus mykiss) and sulfide-tolerant crucian carp (Carassius carassius). In trout RBCs, maximal inhibition of Na+, K+-ATPase was attained at 10 mol l–1 sulfide and amounted to 32% without being influenced by pH between 6.7 and 8.3. Ouabain-resistant K+ influx in the absence and presence of sulfide was insignificant at pH values between 6.7 and 7.7. At higher pH values ouabain-resistant K+ influx increased, but was inhibited to about 15% by 30 mol l–1 sulfide. In RBCs of crucian carp neither Na+, K+-ATPase nor ouabain-resistant K+ influx were affected by sulfide concentrations up to 850 mol l–1. Differences in sulfide-sensitivity of K+ influx between both species can be based upon different properties of the membrane transporter themselves. The reduced Na+, K+-ATPase activity in trout RBCs may also result from a slightly reduced (by 9%) ATP level after sulfide exposure. In addition, intracellular sulfide concentrations were higher in trout RBCs as compared to crucian carp. In trout, intracellular sulfide concentrations reached extracellular levels within 5 min of incubation whereas sulfide concentrations in crucian carp RBCs remained about 2-fold lower than extracellular concentrations. Although the physiological basis of sulfide-insensitive K+ influx in crucian carp RBCs is currently unknown it may contribute to the extremely high sulfide-tolerance of this species.  相似文献   

19.
Detailed measurements of gill area and constituent variables (total filament number, total filament length and mean filament length), and immunolocalization of the α-subunit of Na+/K+-ATPase and Na+/K+-ATPase activity were performed on both hemibranchs of all five arches of freshwater potamotrygonid stingrays (Paratrygon aiereba and Potamotrygon sp.). Both species exhibit similar mass-specific gill area, 89.8 ± 6.6 and 91.5 ± 4.3 mm2 g−1 for P. aiereba and Potamotrygon sp., respectively. The density of Na+/K+-ATPase-rich MRCs and Na+/K+-ATPase activity was higher in the 4th gill arch in both species. The Na+/K+-ATPase activity was positively correlated to the Na+/K+-ATPase-rich (Na+/K+-ATPase rich) mitochondrion-rich cell (MRC) distribution among the gill arches of P. aiereba but not in Potamotrygon sp. The levels Na+/K+-ATPase activity were not correlated to the gill surface area among the arches for both rays’ species. Considering that the Na+/K+-ATPase-rich MRC is the main site for active ion transport in the gill epithelia and Na+/K+-ATPase activity plays a crucial role in osmoionoregulatory function, we suggesting that 4th gill arch is more relevant for osmoregulation and ion balance in these potamotrygonids.  相似文献   

20.
The activity of the enzyme Na+,K+-ATPase and morphological changes of gill chloride cells in grouper, Epinephelus coioides larvae and juveniles were determined 6–48 h after abrupt transfer from ambient rearing conditions (30–32 ppt, 26.5–30 °C) to different salinity (8, 18, 32, 40 ppt) and temperature (25, 30 °C) combinations. Na+,K+-ATPase activity in day 20 larvae did not change at salinities 8–32 ppt. Activity decreased significantly (P <0.01) after exposure to 40 ppt at 25–30 °C, which was accompanied by an increase (P <0.05) in density and fractional area of chloride cells. Enzyme activity in 40 ppt did not reach a stable level and larvae failed to recover from an osmotic imbalance that produced a low survival at 25 °C and death of all larvae at 30 °C. Enzyme activity and chloride cell morphology in day 40 groupers did not change in 8–40 ppt at 25 °C and 8–32 ppt at 30 °C. A significant decrease and a subsequent increase in Na+,K+-ATPase activity in 40 ppt at 30 °C was associated with the increase in chloride cell density resulting in an increased fractional area but a decreased cell size. Enzyme activity and chloride cells of day 60 grouper were unaffected by abrupt transfer to test salinities and temperatures. These results demonstrate that grouper larvae and juveniles are efficient osmoregulators over a wide range of salinities. Salinity adaptation showed an ontogenetic shift as the larvae grew and reached the juvenile stage. This development of tolerance limits may reflect their response to actual conditions existing in the natural environment.  相似文献   

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