Does urea reabsorption occur via the glucose pathway in the kidney of the freshwater rainbow trout?     

Carol?BuckingEmail author  Chris?M.?Wood 《Fish physiology and biochemistry》2004,30(1):1-12

This study tested the hypothesis that the renal reabsorption of urea occurs via the glucose transport pathway in the freshwater rainbow trout (Oncorhynchus mykiss). The relationship between glucose transport and urea transport was examined by experimentally elevating the rate of renal glucose reabsorption via infusion of the fish with exogenous glucose, and by inactivating the glucose transporters via the administration of phlorizin. Under all treatments, urea was reabsorbed against a concentration gradient, with plasma levels of urea being higher than urine levels. Glucose was almost completely reabsorbed (88%) whereas urea was reabsorbed less efficiently (47%) but to a greater extent than water (22%). Glucose and urea reabsorption were both found to be correlated with Na⁺ and Cl^– reabsorption, though the latter were 20 fold and 200–300 fold higher than glucose and urea transport rates, respectively. Glucose infusions greatly increased glucose reabsorption but urea reabsorption was unaffected. Phlorizin treatment completely blocked glucose reabsorption, but urea reabsorption was again unaffected. We conclude that there is no relationship between glucose and urea handling in the trout kidney, thus disproving the hypothesis.  相似文献   

Relationship between otolith and somatic growth:consequence of starvation on acid-base balance inplasma and endolymph in the rainbow trout Oncorhynchus mykiss     

P. Payan  G. Borelli  G. Boeuf  N. Mayer-Gostan 《Fish physiology and biochemistry》1998,19(1):35-41

The effect of a short period of starvation (5–6 weeks) on thechemistry of plasma and inner ear endolymph (Na⁺,K⁺, Cl^-, total Ca, protein, totalCO₂ concentrations and pH) was studied in trout (Oncorhynchusmykiss). In plasma, only total Ca significantly decreased, by 0.17 mM, instarved trout. A slight drop (10%) in the plasma protein content wasalso observed. Starvation induced a metabolic plasma alkalosis characterizedby a non-signifiacant increase in pH and a significant drop of 22% oftotal CO₂. In endolymph, the Na⁺,K⁺, Cl^- , total Ca and protein concentrationswere not significantly different in control and starved trout, but in thelatter, the pH of the endolymph was less alkaline (significant decrease of0.3 UpH) and the total CO₂ concentration was significantlyreduced by 50%. Experimental starvation was selected as aphysiological situation characterized by a slowing down of both somatic andotolith growth. We propose that the reduced rate of otolith growth isdirectly related to an overall reduction in the alkalinity of theendolymph.  相似文献   

Sodium dependent ion transporters in trout gills     

G. Flik  T. Kaneko  A.M. Greco  J. Li  J.C. Fenwick 《Fish physiology and biochemistry》1997,17(1-6):385-396

Biochemical procedures developed to isolate plasma membranes from the branchial epithelium of rainbow trout (Oncorhynchus mykiss) yield membrane fractions that are specifically enriched in the plasma membrane marker enzyme Na⁺/K⁺-ATPase. As the bulk of the branchial Na⁺/K⁺-ATPase is assumed to be confined to the mitochondria-rich chloride cells, such membrane preparations must contain the essence of the enzymatic machinery of the chloride cells. Basal Na⁺ activity in branchial (chloride) cells is around 10 millimolar and, accordingly, we find a K_m for Na⁺ of the Na⁺/K⁺-ATPase of 13 millimolar, indicating that the enzyme may be regulated by changes in cytosolic sodium. The Na⁺-gradient across the serosal plasma membrane created by this pump provides energy for 3Na⁺/Ca²⁺-exchange and bumetanide-sensitive Na⁺/K⁺/2Cl^--cotransport. Here we further postulate the presence of a Na⁺/Cl^--cotransporter, indicated by thiazide-sensitive, bumetanide-insensitive transport of Na⁺ and Cl^-; this cotransporter activity awaits the characterization of its kinetics. The Na⁺/Ca²⁺-exchanger has kinetic characteristics compatible with a regulatory role of cytosolic Na⁺ in the activity of this carrier. Both Na⁺/Ca²⁺-exchange and Ca²⁺-ATPase activity may contribute to transport of Ca²⁺, the former having lower affinity for calcium but a higher capacity than the latter carrier. The Na⁺/K⁺/2Cl^--cotransporter has kinetics that favor a regulatory role for plasma K⁺ in the activity of this carrier. Seawater adaptation leads to increased activity of cotransporter molecules in the plasma membrane fractions (the activity increases relative to that of the Na⁺/K⁺-ATPase) and this may reflect a function in Cl^--extrusion performed by the chloride cells in a seawater environment. A function for the cotransporter in the gills of freshwater fish may be the regulation of cell volume.  相似文献   

Ionoregulatory responses to temperature change in two species of freshwater fish     

R.J. Gonzalez  D.G. McDonald 《Fish physiology and biochemistry》2000,22(4):311-317

We examined the ionoregulatory responses to temperature changes in two species of freshwater fish that differ in thermal preferences; the stenothermal, cold-water rainbow trout (Oncorhynchus mykiss) and the more eurythermal, warm-water common shiner (Notropis cornutus). We found that rainbow trout maintained constant plasma Na⁺ levels over the entire temperature regime (5–20 °C). Upon transfer from 15 °C (holding temperature) to 5 and 10 °C, rainbow trout experienced a significant drop in Na⁺ uptake (J_in ^Na), but after two weeks J_in ^Na had upregulated to warm temperature levels. Further, Na⁺ efflux (J_out ^Na) fell significantly at the colder temperatures. As a result, trout at the lowest temperatures were still in ion balance. When trout were exercised to exhaustion both O₂ consumption (MO₂) and J_out ^Na rose significantly at all temperatures, but while MO₂ continued to be dependent upon temperature, J_out ^Na was high and constant. In contrast to the trout, common shiners experienced a 20% drop in plasma Na⁺ at 5 °C. Upon exposure to cold temperatures they experienced a reduced J_in ^Na, and showed no signs of acclimation during the subsequent two weeks. Likewise J_out ^Na was constant at all temperatures. These findings raise questions regarding the degree to which fish employ homeostatic mechanisms designed to defend a set- point (i.e., steady-state) osmolarity and ionic composition.  相似文献   

Arginine effects on biochemical composition of sperm in rainbow trout,Oncorhynchus mykiss          下载免费PDF全文

Fateme Pourkhazaei  Eisa Ebrahimi  Alireza Ghaedi 《Aquaculture Research》2017,48(7):3464-3471

The present study investigated the effect of arginine on seminal plasma composition in rainbow trout. Male rainbow trout broodstocks (2500 ± 200 g) were fed five practical diets (each consisting of three triplicates) supplemented with Arginine at 0.50%, 1.50% and 2.00%. The control group were fed without arginine. Broodstock feeding lasted for 90 days, and then fish semen was sampled. Results indicated no significant differences in LDH, ALP, Fe²⁺ and phosphorous content among the different treatments. The lowest levels of AST and ALT and the highest levels of Ca²⁺ and Mg²⁺ ions were observed in the treatment fed with 1.50% arginine, which showed significant differences from other treatments (P < 0.05). Moreover, the amount of Cl^?, Na⁺ and K⁺ ions was significantly increased in the seminal plasma in fish fed diets containing arginine in comparison with the control. As the amount of arginine was increased, the levels of uric acid became significantly greater in contrast to urea and glucose levels. The highest amounts of cholesterol, fructose and total protein were observed in treatments fed on 2.00%, 0.50% and 1.00% arginine, respectively, showing significant differences from other treatments (P < 0.05). The highest pH value was assayed in the 1.50% arginine treatment. Results indicated that arginine had a potential efficacy on semen quality in rainbow trout broodstocks.  相似文献   

Vitamin D3 and the renal handling of phosphate in American eels     

J. C. Fenwick  M. G. Vermette 《Fish physiology and biochemistry》1989,7(1-6):351-358

Cholecalciferol (Vitamin D₃) increased plasma inorganic phosphate concentration in American eels,Anguilla rostrata, in a dose-dependent fashion. This response was more marked in phosphate loaded fish. In control as well as phosphate loaded eels the hyperphosphatemic response to D₃ was associated with a sharp reduction in renal phosphate clearance relative to¹⁴C-polyethelene glycol (PEG) clearance. Glomerular filtration and urine flow rates were not affected by D₃. As renal phosphate clearance, even in phosphate loaded eels, never significantly exceeded that of PEG, it is suggested that D₃ reduced the relative clearance rate of phosphate by increasing renal phosphate reabsorption rather than by reducing the tubular secretion of phosphate.  相似文献   

Effects of adrenaline on ionic equilibria in red blood cells of rainbow trout (Salmo gairdneri)     

Thomas A. Heming  David J. Randall  Madeleine M. Mazeaud 《Fish physiology and biochemistry》1987,3(2):83-90

Effects of adrenaline on the equilibrium distributions of Na⁺ , K⁺ , H⁺ , Cl^– , and H₂O across the cell membrane of rainbow trout (Salmo gairdneri) erythrocytes were determinedin vitro, as a function of P CO₂ (1.76–7.77 torr). CO₂-carrying capacity of the blood was also examined. Plasma catecholamine concentrations inunanaesthetized, unrestrained trout were 3.1 nM adrenaline and 1.2 nM noradrenaline. Elevation of the plasma adrenaline concentrationin vitro to 4.6 × 10³ nM resulted in net gains of Na⁺ , Cl^– and H₂O by red cells, a net loss of H⁺ from red cells, and a pronounced red cell swelling. Adrenaline also reduced the CO₂-carrying capacity of trout bloodin vitro. The magnitudes of these effects increased with P_CO2 and, thus, were sensitive to blood HCO₃ ^– concentrations. The distribution of K⁺ between red cells and plasma was unaffected by adrenaline. Adrenergic-mediated ion movements and red cell swelling were sensitive to both propranolol and SITS. These results are consistent with the symport NaCl uptake model for adrenergic-mediated swelling of Baroinet al. (1984). The adrenergic response of fish erythrocytes may function to ameliorate the effects of blood acidoses on O₂-carrying capacity by maintaining red cell pH in the face of a decrease in plasma pH.  相似文献   

Osmoregulation in the mudskipper,Boleophthalmus boddaerti II. transepithelial potential and hormonal control     

C.G.L. Lee  W.P. Low  T.J. Lam  A.D. Munro  Y.K. Ip 《Fish physiology and biochemistry》1991,9(1):69-75

Boleophthalmus boddaerti submerged in 10%, 50% and 80% seawater (sw) for 7 days, had whole body transepithelial potentials (TEP) of 3.3, 18.3 and 22.9 mV, respectively. Hypophysectomy significantly decreased the TEP ofB. boddaerti and reversed the polarity of the TEP of the fish exposed to 10% sw.Hypophysectomy also significantly decreased the branchial Na⁺-K⁺ activated adenosine triphosphatase (Na⁺,K⁺-ATPase) activity but increased the activity of branchial HCO₃ ^–-Cl^– stimulated adenosine triphosphatase (HCO₃ ^–,Cl^–-ATPase) inB. boddaerti exposed to 10% sw. However, survival in 10% sw was not significantly impaired by hypophysectomy and no significant change in plasma osmolality and plasma Na⁺ and Cl^– concentrations was observed.Various doses of ovine-prolactin or salmon-prolactin were unable to restore the TEP of hypophysectomizedB. boddaerti in 10% sw to that of the sham-operated fish. However, cortisol increased TEP to a positive value in hypophysectomizedB. boddaerti, though it was still lower than the sham-operated control. Cortisol treatment also affected the plasma osmolality, plasma Na⁺ and Cl^– contents and branchial Na⁺,K⁺-ATPase and HCO₃ ^–,Cl^–-ATPase activities. Overall, the hormonal control of osmoregulation inB. boddaerti appeared to differ from that of other teleosts.  相似文献   

Antidiuretic action of vasoactive endothelins in the in situ perfused rainbow trout kidney     

J.A. Brown  S. Amer 《Fish physiology and biochemistry》1997,17(1-6):339-345

The present studies examined, for the first time, the renal actions of endothelin-1 (ET-1) and Sarafotoxin S6b (SRTX-6b) (an endothelin-like peptide from snake venom) at 10^-11 M and 10^-9 M, using the in situ perfused kidney of the rainbow trout, Oncorhynchus mykiss. In further studies ET-1 (10^-9 M) was accompanied by Captopril (5 × 10^-4 M) to inhibit angiotensin II formation and determine whether the newly-identified intrarenal renin-angiotensin system (RAS) in the trout kidney was involved in ET-1's actions. These studies demonstrated that ET-1 and SRTX-S6b constrict the trout trunk vasculature, increasing vascular resistance and decreasing perfusate flow rates. Captopril did not affect this response and therefore angiotensin II is not implicated in the vascular responses. Direct action of endothelins on vascular receptors is indicated which, in vivo, is likely to be involved in regulation of renal vascular tone. Both ET-1 and SRTX-6b induced immediate decreases in glomerular filtration rates (GFR) reaching 30% and 34% decrease with 10^-11 M ET-1 and SRTX-6b respectively and 50% and 57% decrease with 10^-9 M ET-1 and SRTX-6b respectively. Urine flow rates decreased to a slightly lesser extent because of decreased tubular reabsorption of water; relative free water clearances increased from approximately 17% to 21% while urine/plasma inulin concentration ratios decreased slightly. This significant depressed urine osmolarity. Captopril completely blocked the effects of endothelins on tubular water reabsorption suggesting intrarenal RAS involvement in this action, although a kinin-mediated effect cannot, at this stage, be excluded. The glomerular antidiuretic action of ET-1 and SRTX-6b partially reflected a decreased population of filtering nephrons (41% filtering in control kidneys, 32–36% filtering in the presence of 10^-11 M M ET-1/SRTX-6b, 31–32% filtering in the presence of 10^-9 M ET-1/SRTX-6b). In addition, 25–40% reductions of single nephron filtration rates were estimated. Glomerular actions of endothelins were partially inhibited by Captopril, suggesting either that renal endothelins have both direct renal actions and secondary effects through activation of the renal RAS, or that kinins can modulate the renal actions of endothelins.  相似文献   

Ammonia and urea excretion in the tidepool sculpin (Oligocottus maculosus): sites of excretion,effects of reduced salinity and mechanisms of urea transport     

P. A. Wright  P. Part  C. M. Wood 《Fish physiology and biochemistry》1995,14(2):111-123

Tidepool sculpins live in a variable environment where water temperature, salinity, gas tensions, and pH can change considerably with the daily tide cycle. Tidepool sculpins are primarily ammoniotelic, with 8–17% of nitrogen wastes excreted as urea. The majority of net ammonia (J^net _amm; 85%) and urea (J^net _urea; 74%) excretion occurred across the gill, with the remainder excreted across the skin, the kidney, and/or gut. Acute (2h) exposure to 50% seawater significantly increased J^net _urea (2.8-fold), but reduced J^net _amm (3.5-fold). In fish exposed to 50% seawater for 1 week, J^net _urea returned to control values, but J^net _amm remained slightly depressed. Unidirectional urea influx (Jⁱⁿ _urea) and efflux (J^out _urea) were measured using¹⁴C-urea to determine if urea was excreted across the gills by simple diffusion or by a carrier-mediated mechanism. Jⁱⁿ _urea increased in a linear manner with increasing urea water levels (0–11 mmol N l^–1), while J^out _urea was independent of external urea concentrations. As well, J^net _urea and J^{out inurea} were not significantly different from one another, indicating the absence of back transport. Urea analogs and transport inhibitors added to the water did not have any consistent effect on unidirectional urea flux. These results demonstrate that ammonia and urea excretion rates and sites of excretion in tidepool sculpins are very similar to those found in other marine and freshwater teleosts. Urea and ammonia may play a role in osmoregulation as excretion rates and tissue levels were influenced by changes in water salinity. Finally, we found no evidence for a specific urea carrier; branchial urea excretion is likely dependent on simple diffusion.  相似文献   

Cortisol treatment improves the development of hypoosmoregulatory mechanisms in the euryhaline rainbow trout,Salmo gairdneri     

Steffen S. Madsen 《Fish physiology and biochemistry》1990,8(1):45-52

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   

Osmoregulation in the mudskipper,Boleophthalmus boddaerti I. Responses of branchial cation activated and anion stimulated adenosine triphosphatases to changes in salinity     

Ip  Y. K.  Lee  C. G. L.  Low  W. P.  Lam  T. J. 《Fish physiology and biochemistry》1991,9(1):63-68

The mudskipperB. boddaerti, was able to survive in waters of intermediate salinities (4–27). Fish submerged in dechlorinated tap water suffered 60% mortality by the fifth day while 60% of those in 100% sea-water (sw) died after the third day of exposure. After being submerged in 50% or 80% sw for 7 days, the plasma osmolality, plasma Na⁺ and Cl^– concentrations and the branchial Na⁺ and K⁺ activated adenosine triphosphatase (Na⁺,K⁺-ATPase) activity were significantly higher than those of fish submerged in 10% sw for the same period. However, the activities of the branchial HCO₃ ^– and Cl^– stimulated adenosine triphosphatase (HCO₃ ^–,Cl^–-ATPase) and carbonic anhydrase of the latter fish were significantly greater than those of the former. Such correlation suggests that Na⁺,K⁺-ATPase is important for hyperosmotic adaptation in this fish while HCO₃ ^–-Cl^–-ATPase and carbonic anhydrase may be involved in hypoosmotic survival.  相似文献   

Hormonal regulation of renal inorganic phosphate transport in the winter flounder, Pleuronectes americanus     

J.L. Renfro 《Fish physiology and biochemistry》1997,17(1-6):377-383

Intestinal uptake and renal excretion are the primary determinants of inorganic phosphate (P_i) balance in teleosts. In general, teleost kidneys may either reabsorb filtered P_i or secrete excess P_i into the urine. Primary monolayer cultures of flounder (Pleuronectes americanus) renal proximal tubule epithelium (PTCs) have helped identify several hormones that may participate in conservation or excretion of P_i. Mounted in Ussing chambers, the monolayer cultures can be used to assay transepithelial P_i transport. Several factors, including metabolic acidosis, elevation of plasma [P_i], salmon stanniocalcin, salmon somatolactin and mammalian prolactin, have now been shown to alter transepithelial P_i transport in winter flounder PTCs. Salmon stanniocalcin (STC) stimulated P_i luminal-to-peritubular transport (reabsorption) at a dosage of 12.5–50 ng/ml (0.25–1.0 nM). Net P_i transport changed within 30 min and progressively increased from slight net secretion in untreated controls to net reabsorption after 3 h. The target and function of somatolactin have been uncertain. In our hands salmon somatolactin (sSL) also stimulated P_i reabsorption by flounder PTCs in a dose-dependent manner at physiological levels of the hormone (12.5 ng/ml). Net P_i transport was significantly altered by sSL within 2 h after the initial exposure. Neither sSL nor STC had any effect on transepithelial Ca²⁺ transport. The effects of both sSL and STC were mimicked by forskolin, whereas H-89, a highly specific protein kinase A inhibitor, significantly decreased the effects of the hormones as well as forskolin-induced P_i reabsorption. Furthermore, the production and release of cAMP were increased more than two-fold following exposure to STC or sSL. The data indicate that STC and sSL directly stimulate net renal P_i reabsorption by a cAMP-dependent pathway. In addition, mammalian prolactin greatly, and salmon growth hormone slightly, increased net P_i reabsorptive flux, whereas salmon prolactin had no effect. These results appear to be related to the location of the cysteine disulfide bonds within the molecular structure. Although somatolactin and stanniocalcin may both stimulate renal P_i conservation, their actions may be related to different physiological conditions.  相似文献   

Ionoregulatory and respiratory responses of brown trout,Salmo trutta,exposed to lethal and sublethal aluminium in acidic soft waters     

Colin P. Waring  J. Anne Brown 《Fish physiology and biochemistry》1995,14(1):81-91

Soft water acclimated (Ca²⁺ 0.02 mM; Na⁺ 0.03 mM; K⁺ 0.01 mM; pH 7.0), cannulated brown trout (Salmo trutta) were exposed to various pH and aluminium (Al) regimes (pH 7.0, pH 5.0, pH 5.0 plus Al: 50, 25, and 12.5 g l^–1) for up to 5 days in order to determine (i) the sublethal concentration of Al at pH 5.0 for this species (ii) their ionoregulatory and respiratory status. No mortality or physiological disturbances were evident at pH 7.0 or pH 5.0. All trout died within 48 h at pH 5.0 in the presence of Al at 50 g l^–1 and 67% died over the 5 day period at pH 5.0 in the presence of Al at 25 g l^–1. Fish at these lethal Al concentrations showed significant decreases in arterial blood oxygen content (C_aO₂) but no changes in plasma osmolarity or the concentrations of plasma Na⁺, K⁺ and Cl^–. Physiological disturbance was more marked at the 50 g l^–1 Al concentration. The surviving fish at 25 g l^–1 showed few signs of physiological recovery while continually exposed to this regime. No fish died during the exposure to water of pH 5.0 containing 12.5 g l^–1 Al, but physiological disturbance was still apparent. These sublethally-stressed trout showed a transient decline in the plasma concentrations of Na⁺ and Cl^–1. Although C_aO₂ decreased, recovery was evident. The data suggest that in the brown trout, environmental Al concentration is as important as pH and calcium concentration in determining the physiological status of the fish.  相似文献   

Effects of growth hormone on plasma ionic regulation,respiration and extracellular acid-base status in trout (Oncorhynchus mykiss) transferred to seawater     

H. Seddiki  V. Maxime  G. Boeuf  C. Peyraud 《Fish physiology and biochemistry》1995,14(4):279-288

The effects of trout recombinant growth hormone (rtGH) treatment (0.25 g g^–1 by intraperitoneal implant) on plasma ionic regulation, extracellular acid-base status and respiration were investigated in freshwater rainbow trout and during a 4-day period after direct transfer into seawater (35 g 1^–1).In freshwater, rtGH treatment resulted in a significant increase in gill (Na⁺, K⁺) ATPase activity and in standard metabolism (MO₂). The latter would mainly result from a higher rate of protein synthesis. Direct transfer from freshwater to seawater induced a decrease in arterial blood pH, far more pronounced in controls than in treated fish. This effect could be regarded in both groups mainly as a metabolic acidosis resulting from extracellular ion composition changes (i.e., an increase higher in chloride than in sodium, more marked in controls than in treated fish). As the rise in PaCO₂, in spite of an increase in ventilatory activity, is more significant in controls than in treated fish, it can be assumed that rtGH treatment lightened the decrease in the gas diffusing capacity of gills induced by transfer to seawater. The initial increase in MO₂ in both controls and treated fish could be the consequence of an increase in energetic cost of ventilation and osmoregulation. Then, in treated fish, the persistent high level of M may indicate a stimulation of intermediary metabolism by rtGH. In addition, the absence in treated fish of an increase in plasma lactate concentration, as observed in controls, would indicate that rtGH attenuated the decrease in O₂ affinity of haemoglobin foreseeable from the metabolic acidosis.This article is dedicated to Professor Claude Peyraud, whose recent death has deeply saddened us. We respectfully pay a tribute to his memory.  相似文献   

Response of rainbow trout gill (Na++K+)-ATPase and chloride cells to T3 and NaCl administration     

Fabiana Trombetti  Vittoria Ventrella  Alessandra Pagliarani  Rodolfo Ballestrazzi  Marco Galeotti  Gianni Trigari  Maurizio Pirini  Anna Rosa Borgatti 《Fish physiology and biochemistry》1996,15(3):265-274

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   

Quantification of presumptive Na+/H+ antiporters of the erythrocytes of trout and eel     

Scott D. Reid  Steve F. Perry 《Fish physiology and biochemistry》1994,12(6):455-463

The presumptive Na⁺/H⁺ exchange sites of trout and eel erythrocytes were quantified using amiloride-displaceable 5-(N-methyl-N-[³H]isobutyl)-amiloride (³H-MIA) equilibrium binding to further evaluate the mechanisms of i) hypoxia-mediated modifications in the trout erythrocyte -adrenergic signal transduction system and ii) the marked differences in the catecholamine responsiveness of this system between the trout and eel. MIA was a more potent inhibitor of both trout apparent erythrocyte proton extrusion (IC₅₀ = 20.1 ± 1.1 mol l^–1, N = 6) activity (as evaluated by measuring plasma pH changes after addition of catecholamine in vitro) and specific ³H-MIA binding (IC₅₀ = 257 ± 8.2 nmol l^–1, N = 3) than amiloride, which possessed a proton extrusion IC₅₀ of 26.1 ± 1.6 mol l^–1 (N = 6) and a binding IC₅₀ of 891 ± 113 nmol l^–1 (N = 3). The specific Na⁺ channel blocker phenamil was without effect on adrenergic proton extrusion activity or specific ³H-MIA binding. Trout erythrocytes suspended in Na⁺-free saline and maintained under normoxic conditions possessed 37,675 ± 6,678 (N = 6) amiloride-displaceable ³H-MIA binding sites per cell (B_max, presumptive Na⁺/H⁺ antiporters) with an apparent dissociation constant (K_D) of 244 ± 29 nmol l^–1 (N = 6). Acute hypoxia (PO₂ = 1.2 kPa; 30 min) did not affect the K_D, yet resulted in a 65% increase in the number of presumptive Na⁺/H⁺ antiporters. Normoxic eel erythrocytes, similarly suspended in Na⁺-free saline, possessed only 17,133 ± 3,716 presumptive Na⁺/H⁺ antiporters (N = 6), 45% of that of trout erythrocytes, with a similar K_D (246 ± 41 nmol l^–1, N = 6). These findings suggest that inter- and intra-specific differences in the responsiveness of the teleost erythrocyte -adrenergic signal transduction system can be explained, in part, by differences in the numbers of Na⁺/H⁺ exchange sites.  相似文献   

Morphological responses of the rainbow trout (Oncorhynchus mykiss) gill to hyperoxia,base (NaHCO3) and acid (HCl) infusions     

Greg G. Goss  Chris M. Wood  Pierre Laurent  Steve F. Perry 《Fish physiology and biochemistry》1994,12(6):465-477

Marked morphological responses occur in the gills of freshwater rainbow trout in response to experimental acid-base disturbance and these responses play an important role in acid-base correction. Compensated respiratory acidosis induced by 70h exposure to environmental hyperoxia (elevated water PO₂) caused a 33% decrease in branchial chloride cell fractional surface area (CCFA). Metabolic alkalosis induced by normoxic recovery (6h) from hyperoxia (72h) caused a 50% increase in CCFA, whereas metabolic alkalosis induced by infusion (19h) of NaHCO₃ caused a 70% rise. However, the largest increase (135%) in CCFA was seen in response to infusion (19h) of HCl. NaCl infusion had no effect. A particular goal was to assess the relative importance of changes in CCFA vs. changes in internal substrate (HCO₃ ^–) availability in regulating the activity of the branchial Cl^–/HCO₃ ^– exchange system. For each of the experimental treatments, the accompanying blood acid-base status and branchial transport kinetics (K_m, J_max) for Cl^– uptake had been determined in earlier studies. In the present study, a positive linear relationship was established between CCFA and J^Cl– _max in individual control fish in the absence of an acid-base disturbance. By reference to this relationship, observed changes in J^Cl– _max during metabolic acid-base disturbances were clearly due to changes in both CCFA and internal substrate levels (plasma [HCO₃ ^–]) with the two factors having approximately equal influence.  相似文献   

Intestinal HCO3− secretion in marine teleost fish: evidence for an apical rather than a basolateral Cl−/HCO3− exchanger     

M. Grosell  C.N. Laliberte  S. Wood  F.B. Jensen  C.M. Wood 《Fish physiology and biochemistry》2001,24(2):81-95

Intestinal fluid was collected from 11 marine teleost fish from the Baltic sea and the Pacific ocean. The anterior, mid and posterior segments of the intestine contained 33–110 mM of HCO₃ ^– equivalents (with exception of the Atlantic cod which contained only 5–15 mM). Considering literature values of transepithelial potentials and concentration gradients, these high levels of HCO₃ ^– equivalents are probably the result of active HCO₃ ^– transport. Possible HCO₃ ^– transport mechanisms were studied in the Pacific sanddab (Citharichthys sordidus) in vitro. Measurements of net secretion of HCO₃ ^– equivalents across the intestinal epithelium revealed mucosal DIDS sensitivity (10^–4 M) and Cl^–-dependence of the HCO₃ ^– equivalent net flux, but no serosal DIDS (10^–4 M) sensitivity. Net Na⁺ uptake was abolished in the absence of Cl^–, but some Cl^– uptake persisted in the absence of Na⁺, at a rate similar to that of net HCO₃ ^– secretion. Anterior, mid and posterior segments of the intestine performed similarly. These observations support the presence of an apical rather than a basolateral Cl^–/HCO₃ ^– exchanger and thus contrast the currently accepted model for intestinal HCO₃ ^– secretion. This apical Cl^–/HCO₃ ^– exchanger alone, however, is not sufficient for maintaining the observed HCO₃ ^– equivalents gradient in vivo. We suggest a coupling of cytosolic carbonic anhydrase, a basolateral proton pump and the apical Cl^–/HCO₃ ^– exchanger to explain the intestinal HCO₃ ^– transport.  相似文献   

Enhanced hypoosmoregulatory response to growth hormone after cortisol treatment in immature rainbow trout,Salmo gairdneri     

Steffen S. Madsen 《Fish physiology and biochemistry》1990,8(4):271-279

The growth-independent effect of ovine growth hormone (oGH) and oGH + cortisol treatment on seawater (SW) adaptation in immature rainbow trout, Salmo gairdneri was investigated. Fish were injected every second day with saline, 2.0 μg oGH/g or 2.0 μg oGH + 8.0 μg cortisol/g for a maximum of 8 injections in freshwater (FW). Subgroups were transferred to 28‰ SW after 4 or 8 injections, and changes in plasma Na⁺ and Cl⁻, muscle water content and gill Na⁺/K⁺-ATPase activity were measured. In both of the hormone-treated groups retained in FW, gill Na⁺/K⁺-ATPase activity and interlamellar chloride cell density increased. The effects were most pronounced in the oGH + cortisol group after 2 weeks of treatment. After transfer to SW most of the control fish died due to the osmotic stress, whereas in the hormone-treated groups, mortality was low and there was a positive correlation between pretransfer gill Na⁺/K⁺-ATPase and the ability to maintain ionic-osmotic homeostasis after SW transfer. After two weeks of oGH + cortisol treatment, gill Na⁺/K⁺-ATPase activity was maximal. In contrast, after SW transfer, Na⁺/K⁺-ATPase activity increased further in the oGH-treated group. This group regulated ionic-osmotic parameters less effectively than the oGH + cortisol-treated group. The data indicate that GH and cortisol are important hormones in the regulation of hypoosmoregulatory mechanisms in S. gairdneri.  相似文献