Serum ions concentration and atpase activity in gills,kidney and oesophagus of european sea bass (Dicentrarchus labrax,pisces, perciformes) during acclimation trials to fresh water

• 1.1. Kidney, oesophagus and gill Na⁺-K⁺ ATPase activity and serum Na⁺, K⁺ and Cl⁻ concentrations are evaluated in European sea bass during experimental acclimation to fresh water.
• 2.2. Kidney and oesophagus ATPase increase in low salinity and reach a maximum in fresh water.
• 3.3. Gill ATPase decreases during the acclimation trials and rises again to normal values after a 3-week stay in fresh water.
• 4.4. Na⁺ and K⁺ serum concentrations decrease during the trials and increase back after a 3-week stay in fresh water.
• 5.5. The correlations between enzymatic activities, serum ion concentrations, morphological changes and environmental salinity are discussed.

     

Nacl flux in the flounder (Pseudopleuronectes americanus) intestine: Effects of ph and transport inhibitors

• 1.1. The effects of extracellular pH on Na⁺ and Cl⁻ absorption were studied in vitro in the small intestine of the winter flounder, Pseudopleuronectes americanus.
• 2.2. Reductions in bathing solution pH inhibited J_ms^na (mucosal-to-serosal flux) and J_net^na (net flux) (r = 0.90) and J_net^Cl (r = 0.92) [due to an increase in J_sm^Cl, (serosal-to-mucosal)] and decreased short circuit current (Isc).
• 3.3. Luminal bumetanide (0.1 mM) and amiloride (1 mM) inhibited Na⁺ and Cl⁻ absorption by reducing J_ms.
• 4.4. Luminal barium (5mM) and luminal copper (100 μM) decreased J_ms^Cl and increased J_sm^Cl.
• 5.5. We conclude that reductions in extracellular pH inhibit a luminal membrane NaCl absorptive process (Na⁺-K⁺-2Cl⁻) and stimulate an electrogenic Cl⁻ secretory process.

     

Cationic and anionic channels of apical receptive membrane in a taste cell contribute to generation of salt-induced receptor potential

• 1.1. After ionic composition of superficial fluid (ISF) and interstitial fluid (ISF) of the frog Rana catesbeiana) tongue had mostly been changed with a low Na⁺ saline solution, the relations between membrane potentials and receptor potentials in a frog taste cell evoked by various concentrations of NaCl and various types of salts were analyzed to examine permeability of the taste receptive membrane to cations and anions.
• 2.2. The mean reversal potentials for depolarizing potentials of a taste cell in response to 0.05 M, 0.2 M and 0.5 M Nad were -40.0, 6.4 and 28.8 mV, respectively.
• 3.3. When adding an anion channel blocker, SITS, to a NaCl solution the reversal potential for receptor potential with NaCl plus SITS became about twice as large than with NaCl alone.
• 4.4. Reversal potentials for 0.2 M NaCl, LiCl, KCl and NaSCN were 6.4, 25.4, −1.0 and −7.8 mV, respectively, indicating that permeability of the apical taste receptive membrane to cations of Cl⁻ salts is arranged in the order of Li⁺ > Na⁺ > K⁺ and that the permeability to anions of Na⁺ salts is arranged as SCN⁻ > Cl⁻
• 5.5. It is concluded that in the case of NaCl stimulation, Na⁺ and Cl⁻ of NaCl stimulus permeate NaCl-gated cationic and anionic channels at the apical taste receptive membrane in generating receptor potentials.

     

Effects of water stress on hemolymph volume,osmotic potential and chemical composition in Megetra cancellata

• 1.1. Rates of water loss in Megetra cancellata were very high compared to those reported for other xeric arthropods.
• 2.2. Hemolymph weight in hydrated animals was 43.0% of the total body weight while it was 24.7% in desiccated animals that had lost 16.1% of their body weight as water.
• 3.3. Hemolymph osmotic potential increased from 417 to 447 mOsm/kg in desiccated beetles, but osmotic regulation was evident.
• 4.4. Total hemolymph protein mass and concentration decreased in desiccated beetles while amino acid concentrations remained constant (at about 70 mM).
• 5.5. Na⁺ and −PO₄ concentrations increased in desiccated beetles.
• 6.6. Cl⁻ and K⁺ concentrations in desiccated beetles were equal to those in undesiccated beetles.

     

Intestinal l-methionine transport in the cultured gilthead bream (Sparus aurata)

• 1.1. The influx and transepithelial movements of l-methionine and its effects on the electrophysiology and Na-Cl-transport in upper and lower intestine of the cultured fish, Spanis aurata, were measured.
• 2.2. The K_m and V_max of l-methionine influx into the tissues were higher in lower intestine than in upper intestine. A prominent diffusion-like transport component was also measured in both segments during influx experiments.
• 3.3. Net transepithelial fluxes of l-methionine (1 mM) were observed in both upper and lower intestine, this transport being Na⁺-dependent.
• 4.4. The two intestinal segments exhibited an electrical potential difference (PD) and a short circuit current (I_sc) serosa negative or near zero. Tissue conductance (G_t) was higher in posterior than in lower intestine.
• 5.5. Addition of l-methionine to the mucosal side of lower or upper intestine did not induce changes in PD in either part.
• 6.6. Isotopic fluxes of Cl⁻ or Na⁺ measurements under short circuit conditions showed that there were no net Cl⁻ or Na⁺ transport in either part.
• 7.7. l-Methionine additions to the mucosa did not induce changes in unidirectional fluxes of Cl⁻ or Na⁺ or in the (I_sc) in either the anterior or posterior intestine.

     

Osmoregulation in the brook trout,Salvelinus fontinalis—II. Effects of size,age and photoperiod on seawater survival and ionic regulation

• 1.1. Brook trout (Salvelinus fontinalis) of a single genetic stock, and hatched at the same time, were raised under two photoperiod and two feeding regimes to obtain fish of the same age but with different sizes and photoperiod experiences. In 11 experiments over 1.5 firs, fish were gradually exposed to 32 ppt seawater for 20 days to investigate the ontogeny of salinity tolerance.
• 2.2. Daily changes in plasma osmolarity, [Na⁺], [Cl⁻], [K⁺], [Mg²⁺], thyroxine, hematocrit and gill Na⁺,K⁺-ATPase during adaptation to 10, 20 and 32 ppt were examined in one experiment.
• 3.3. Size was the primary determinant of seawater survival (r² = 0.77) the effect of size on seawater survival slowed after fish reached a fork length of 14 cm. The effect of age on seawater survival (r² = 0.65) was through its covariance with size.
• 4.4. Photoperiod affected seawater survival only through its influence on the timing of male maturation, which decreased salinity tolerance.
• 5.5. Regulation of plasma osmolarity, [Na⁺], [Cl⁻], [K²⁺], [Mg²⁺] and hematocrit in sea water increased linearly with size over the entire range of sizes (6–32 em).
• 6.6. Gill Na⁺,K⁺-ATPase activity after 20 days in seawater decreased with increasing size of brook trout, possibly reflecting decreased demand for active ion transport in larger fish.
• 7.7. Plasma thyroxine concentrations declined in seawater, but no definitive role of this hormone in seawater adaptation was found.
• 8.8. Size dependent survival and osmoregulatory ability of brook trout is compared to other salmonids and a conceptual model is developed.

     

The effect of eyestalk ablation on growth,haemolymph composition and gill Na+, K+-ATPase activity of Penaeus monodon juveniles

• 1.1. Eyestalk unablated and unilaterally ablated Penaeus monodon juveniles had survival rates after 5 months of 75–72.5 and 67.5–60%, respectively.
• 2.2. Unilaterally ablated shrimps had significantly higher (P < 0.05) growth rate than unablated shrimps.
• 3.3. Eyestalk-ablatement resulted in a decrease in the haemolymph sodium concentration and an increase in the potassium and calcium concentration of shrimps.
• 4.4. The osmolarity of haemolymph and total protein concentration of unablated shrimps were demonstrated to be higher than those of unilaterally ablated shrimps.
• 5.5. The eyestalk-ablated shrimps possess higher total ATPase and Na⁺,K⁺-ATPase activities in the gill than those of unablated shrimps.

     

Cl− fluxes across isolated,perfused gills of the chinese crab Eriocheir sinensis (M.Edw.) acclimated to fresh water

• 1.1. The movements of Cl⁻¹ have been studied in the so-called anterior and posterior gills of E. sinensis using radioactive ³⁶Cl⁻¹.
• 2.2. The anterior gills hardly show any significant movements of Cl⁻¹. They thus have a very low (if any) permeability to that ion. On the contrary, the posterior gills show both passive fluxes and an active inward movement of Cl⁻¹.
• 3.3. The Cl⁻¹ influx in the posterior gills is largely sensitive to the amount of K⁺ in the perfusion saline.

     

Osmoregulation in the brook trout,Salvelinus fontinalis—I. Diel,photoperiod and growth related physiological changes in freshwater

• 1.1. Brook trout (Salvelinus fontinalis) raised from eggs under two photoperiod and two feeding regimes were tested for physiological changes preparatory for transition from freshwater to seawater. Size, age, growth rate, photoperiod, and diel rhythms were examined for possible influences on plasma osmolarity, [Na⁺], [Cl⁻], [K⁺], [Mg²⁺], thyroxine concentration, hematocrit, and gill Na⁺, K⁺-ATPase activity of brook trout in freshwater.
• 2.2. Significant diel cycles were found in plasma osmolarity, [Na⁺] and thyroxine concentration.
• 3.3. Significant size and/or age related changes occurred for plasma osmolarity, Na⁺], [K⁺] and hematocrit, but could explain little of their total variation (0.02 < r² < 0.18).
• 4.4. A sexually dimorphic response to photoperiod was observed in hematocrit for both mature and immature fish, with hematocrit of mature females declining in autumn and hematocrit of immature males increasing in autumn.
• 5.5. Gill Na⁺, K⁺-ATPase activity did not respond to photoperiod or feeding treatment and showed no change with size or age.
• 6.6. Plasma thyroxine levels responded to feeding and photoperiod treatment. There was a significant correlation between the percent mean difference in plasma thyroxine and the mean difference in growth rate between high and low feed fish (r² =0.51), suggesting a relationship between thyroxine and growth.

     

Sodium and potassium balance of captive meadow voles (Microtus pennsylvanicus) fed laboratory chow and vegetation diets

• 1.1. Mineral balance was studied in meadow voles (Microtus pennsylvanicus) maintained in the laboratory.
• 2.2. Urine and fecal Na⁺ contents of voles on low-Na⁺ diets were comparable to those reported for other herbivore species, but urine and fecal K levels were higher.
• 3.3. Voles approached Na⁺ balance (input = output) on diets with Na⁺ content as low as 56 ppm.
• 4.4. There was not a clearcut hypertrophy of the adrenal-gland zona glomerulosa in voles maintained on low-Na⁺ diets.
• 5.5. Plasma K content and bone water content were higher in voles maintained on high-Na ⁺ vegetation diets, suggesting expansion of extracellular fluid volume.

     

Sodium transport in red blood cells of lamprey LAmpetra fluviatilis

• 1.1. Unidirectional Na⁺ influx in lamprey red blood cells was determined using ²²Na as a tracer.
• 2.2. Total Na⁺ uptake and amiloride-inhibitable Na⁺ influx increased in a saturable fashion as a function of external Na⁺ concentration (Na_e).
• 3.3. At 141 mM Na_e, the average value of net Na⁺ influx was 13 ± 1.1 and the amiloride-sensitive Na⁺ influx was 5.3±1.1 mmol/l cells per hr (±SE).
• 4.4. The amiloride-sensitive component of Na⁺ influx was significantly activated by 10⁻⁵ M isoproterenol, by 2 × 10⁻⁵ M DNP, and by cell shrinkage.
• 5.5. Furosemide (1 mM) had no effect on the Na⁺ transport in red cells.
• 6.6. The residual amiloride-insensitive component of Na⁺ transport was a linear function of Na_e in the range of 5–141 mM. This transport seems to be accounted for by simple diffusion.

     

The effect of salinity on coelomic fluid osmolyte concentration and intracellular water content in Luidia clathrata (Say) (Echinodermata: Asteroidea)

• 1.1. The concentrations (mM) of osmolytes in the coelomic fluid of Luidia clathrata kept at 25‰S seawater (control individuals) were: 345, Na⁺; 10, K⁺; 10, Ca²⁺; 44, Mg²⁺; 387, Cl⁻; 0.67, amino acids; 0.09, NH₄⁺.
• 2.2. When individuals were transferred from 25‰S to 15‰S or 35‰S, the concentrations of inorganic ions in the coelomic fluid usually equilibrated within 24hr and became the same as those in the medium.
• 3.3. The intracellular water content (g intracellular H₂O/g solute-free dry tissue) of the pyloric caeca and tube feet of control individuals throughout the experiment was 2.13 and 5.40, respectively.
• 4.4. In tissues of individuals transferred to 15‰S, the intracellular water content increased by an average 50% in 12 hr but returned to 19% above control levels during 1 week.
• 5.5. In tissues of individuals transferred to 35‰S, the intracellular water content decreased by an average 17% in 12 hr and did not change during 1 week.
• 6.6. Luidia clathrata is an osmoconformer and partial cell volume regulator within the seasonal salinity range it encounters.

     

An insect epidermal cell line (UMBGE-4): Structural and electrophysiological characterization

• 1.1. The cellular organization (including junctional connectivity) and electrophysiological characteristics of the UMBGE-4 epithelial cell line originally derived from the cockroach were studied. These cells grew in culture in the form of hollow vesicles which could reach 5 mm in diameter. The wall of the vesicles varied in form and thickness from resembling a squamous to a columnar epithelium. Parts of the vesicle wall were multi-cellular with some cytoplasmic variability in the constituent cells. On the whole, the cellular architecture of the vesicles resembled that of a secretary epithelium with abundant microvilli and apical vacuoles, an extensive network of endoplasmic reticulum and prominent Golgi apparatus.
• 2.2. The main type of cell junction was septate-like and comprised extensive, convoluted regions of cellular apposition with some gap junctions therein. The septate junctions were permeated extensively by lanthanum and the epithelium appeared to be leaky.
• 3.3. A small negative trans-cellular (lumen) potential (mean value, −2.7 mV) was present and this was only transiently affected by changes in extracelluar Na⁺, K⁺ or Cl⁻ concentrations.
• 4.4. The cells' resting membrane potentials were distributed normally around a mean of − 77 mV. Some 64% of resting membrane electrogenesis could be accounted for in terms of K⁺ and Cl⁻ permeabilities; Na⁺ had no involvement.
• 5.5. The structural, electrophysiological and biochemical characteristics taken together would suggest that the UMBGE-4 cells could serve as a useful model for the epidermal epithelium in insects.

     

Mg2+-dependent (Na+ + K+)- and Na+-ATPases in the kidneys of the gilthead bream (Sparus auratus L.)

• 1.1. The (Na⁺ + K⁺)- and Na⁺-ATPases, both present in kidney microsomes of Sparus auratus L., have different activities and optimal assay conditions as, in the first of the two stocks of fish used (A), the spec. act. of the former is 51.7 μmol P_i mg prot⁻¹ hr⁻¹ at pH 7.5, 100 mM Na⁺, 10 mM K⁺, 17.5 mM Mg²⁺, 7.5 mM ATP and that of the latter is 6.5 μmol P_i mg prot⁻¹ hr⁻¹ at pH 6.5, 40 mM Na⁺, 4.0 mM Mg²⁺, 2.5 mM ATP.
• 2.2. Ouabain and vanadate specifically inhibit the (Na⁺ + K⁺)-ATPase but not the Na⁺-ATPase that is preferentially inhibited by ethacrynic acid.
• 3.3. While the (Na⁺ + K⁺)-ATPase is strictly specific for ATP and Na⁺, Na⁺-ATPase can be activated by various monovalent cations and, apart from ATP, hydrolyses CTP, though less efficiently.
• 4.4. The second stock B, subjected to higher salinity than A, shows an acidic shifted Na⁺-ATPase optimal pH, opposed to the stability of that of the (Na⁺ + K⁺)-ATPase, a decreased (Na⁺ + K⁺)-ATPase and a strikingly depressed Na⁺-ATPase.
• 5.5. The results are compared with literature data and discussed on the basis of the presumptive different roles as well as functional prevalence in various salinities of the two ATPases.

     

Ouabain sensitive Na+/K+-transporting ATPase from the brain of Poekilocerus bufonius

• 1.1. The properties of Na⁺/K⁺-transporting ATPase in microsomal fractions from the nervous tissue of the grasshopper, Poekilocerus bufonius were investigated.
• 2.2. Two components of ATPase activity are present.
• 3.3. Inclusion of 1 mM ouabain in the incubation media reduced the activity of total and Na⁺/K⁺-ATPase by 57 and 79%, respectively.
• 4.4. The maximum velocity (V_max) was decreased by the addition of 1 mM ouabain, whereas the apparent K_m value was not affected indicating a non-competitive type of inhibition.
• 5.5. The calculated value of the pI₅₀ was 6.4 (I₅₀ = 3.98 × 10⁻⁷M) for ouabain inhibition of the enzyme showing great sensitivity to the cardiac glycoside ouabain.
• 6.6. The present results show that the physicochemical properties of Na⁺/K⁺-transporting ATPase from the brain of P. bufonius are essentially the same as for the enzyme prepared from the excretory system of the insect which has been previously investigated.
• 7.7. Dissimilarities were also observed between these tissues in the way that the enzyme from the brain was sensitive to ouabain inhibition with a non-competitive type rather than a ouabain-resistance and a competitive type of inhibition for the enzyme from the excretory system.
• 8.8. These dissimilarities are probably due to different isoenzyme patterns available in the same insect.

     

Protein digestion and ion concentrations in rainbow trout (Salmo gairdnerii Rich.) digestive tract in sea- and fresh water

• 1.1. Rainbow trout maintained in fresh water or Actapted to sea-water for 24 hr were fed casein-based dry diet. After feeding, fish were kept in fresh water (FW) or transferred to artificial sea-water (SW) and sacrificed after 10 or 20 hr.
• 2.2. The digestive tract was separated into five parts: stomach, pyloric caeca region, middle intestine and two equal lengths of rectum.
• 3.3. The content of these parts was analysed for ions Na⁺, K⁺, Cl⁻, Mg²⁺ and for free, peptide and total amino acids.
• 4.4. In the fish stomach all ions, with the exception of Ca²⁺, indicate drinking of sea-water. In the pyloric caeca region Na⁺ appears to be efficiently absorbed in SW fish but influxed in FW fish. In the rectum of SW fish K⁺ appears to be reabsorbed but Na⁺ concentrated in faeces.
• 5.5. Free amino acid concentrations were always higher in gut lumen of SW than in FW fish in respect to time after feeding and portion of intestinal content. Free amino acids constitute at most 7.4–8.7% of total amino acids in the content of pyloric caeca region.
• 6.6. Peptide amino acids, being mostly di-, tri- and tetra-peptides, increased in stomach content from 14.7 to 28.4% of the total, from 6 to 10 hr after a meal in SW fish. Peptide amino acids constituted 80.3–89.0% of total amino acids in intestinal content of the pyloric caeca region. These peptide portions decreased in the mid-intestine (47.5–52.5%) and increased again in the rectum (73.6–76.0%).
• 7.7. It was concluded that in rainbow trout fed in both sea- or fresh water, ion concentrations do not seem to interfere with protein digestion and nutrient absorption in alimentary tract.

     

Na+-K+ ATPase and carbonic anhydrase activities in larvae,postlarvae and adults of the shrimp Penaeus japonicus (Decapoda,Penaeidea)

• 1.1. Activities of Na⁺-K⁺ ATPase and carbonic anhydrase were measured through the early post-embryonic development of Penaeusjaponicus. In adults, only the Na⁺-K⁺ ATPase activity was measured.
• 2.2. ATPase activity was variable in the successive development stages. From zero in nauplii, the activity slightly increased in zoeae, and rose sharply in mysis stages 2 and 3.
• 3.3. A further significant increase in activity was noted at the transition from late mysis to early postlarvae, concomitant with a change from the larval osmoconforming pattern of osmoregulation to the postlarval and adult hyper-hyporegulating pattern.
• 4.4. The activity of Na⁺-K⁺ ATPase, measured in isolated cephalothorax, increased from PL3 to PL4 to its maximum value in PL5; at this stage, osmoregulatory capacity was fully efficient.
• 5.5. In young stages of P. japonicus, the variations in Na⁺-K⁺ ATPase activity appear correlated with the development of osmoregulatory ultrastructures, and with osmoregulation and salinity tolerance.
• 6.6. These results are discussed with regard to their ecological and physiological implications.
• 7.7. In adults, the activity of Na⁺-K⁺ ATPase was high in gills and epipodites and no activity was detected in branchiostegites. These results are related to the ultrastructure of these organs.
• 8.8. The activity of carbonic anhydrase did not change significantly in larval and postlarval stages.
• 9.9. From these results, it is proposed that the effector sites of osmoregulation are located in branchiostegites, pleurae and epipodites in postlarvae, and in epipodites and mainly in gills in adults.

     

Sodium-dependence of amino acid transport by the nephridia of Sabella pavonina (annelida,polychaeta)

• 1.1. In the absence of sodium, the reabsorption rate of amino acid α-aminoisobutyric acid (AIB) by the nephridia of Sabella pavonina is reduced to 20% and the AIB accumulation in the cells is reduced to 10%. These results suggest the presence of sodium-dependant processes.
• 2.2. The observed processes are reversible when control conditions are re-established.
• 3.3. A minimum of 17mEq/l Na⁺ is required to restore the normal reabsorption rate.
• 4.4. The addition ofamiloride (10⁻³⁵ M) decreases the reabsorption rate, but to a lesser extent than the absence of sodium.

     

Hemolymph osmo-ionic concentrations in terrestrial crabs following desiccation

• 1.1. The hemolymph osmotic, Na⁺ K⁺, Ca⁺⁺ and Mg⁺⁺ concentrations were determined for both sexes in crabs from mangrove Ucides cordatus and Goniopsis cruentata and supralittoral Ocypode quadrala after aerial desiccation, for 10 hr.
• 2.2. There was no difference between sexes in the two mangrove crabs, but in O. quadrata the females were the most significantly affected (P < 0.01).
• 3.3. Hemolymph osmotic Na⁺, Ca⁺⁺ and Mg⁺⁺ concentrations increased significantly in desiccated ghost crabs, while K ⁺ concentration was not significantly changed. In the two mangrove crabs, only hemolymph Ca⁺⁺ concentration increased significantly, after desiccation.
• 4.4. The short time desiccation is suggested to be a device to study the steps of osmo-ionic regulation in terrestrial crabs.

     

Tetanus responses under rapid bath solution change: Electrotonic depolarization of transverse tubules may release Ca2+ from sarcoplasmic reticulum of Rana japonica skeletal muscle

• 1.1. Single skeletal muscle fibers were transferred from a normal Ringer solution to Na⁺ ion free solution, and vice versa, and tetanus responses were recorded immediately after the transfer.
• 2.2. Fractional tetanus tension recorded immediately after the displacement from the Na⁺ ion free solution to normal Ringer solution was dependent on fiber diameter.
• 3.3. Diffusion of Na⁺ ions along the transverse tubules was simulated [apparent diffusion constant was 3.11 × 10⁻⁶ (cm²/s)].
• 4.4. Our results suggest that the electrotonic spreading of membrane potential, caused by an action potential in the transverse tubules, could release Ca²⁺ ions from sarcoplasmic reticulum.