Osmolality and electrolyte concentration of hemolymph and the problem of ion and volume regulation of cells in higher insects

• 1.1. The study was carried out on 22 species of insects from 5 orders. The osmolality of their hemolymph varied from 319 to 421 mOsm/kg H₂O, concentration of Na⁺ 4.6 to 118 mM/l, K⁺ 6.3 to 73mM/l, Ca²⁺ 3.6 to 12.9 mM/l, Mg²⁺ 2.3 to 76 mM/l. The most abundant cation in the hemolymph of insects from higher orders is either K⁺ or Mg²⁺.
• 2.2. In the muscles of lower and higher insects K⁺ is usually within 80–120 mM/kg wet wt.
• 3.3. Most Ca²⁺ and Mg²⁺ in hemolymph is bound with protein and low molecular anions, concentration of free Ca²⁺ is 0.9-2.1mM/l Mg²⁺ 3.7–8.0 mM/l.
• 4.4. It is concluded that, in insects, potassium hemolymph, cell volume regulation and accumulation of ions in the cell, are ensured by an increased osmolality of hemolymph due to a high percentage contribution of low molecular organic substances which are retained in the hemolymph due to the absence of filtration apparatus in the Malpighian tubules.

     

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.

     

A comparison of the effect of alternating current electronarcosis,rectified current electronarcosis and chemical anaesthesia on the blood physiology of the freshwater bream Oreochromis mossambicus (peters)—III. The effect on the plasma electrolytes Ca2+, Na+ and K+ and on the osmotic pressure of the blood

• 1.1. The effects of alternating current electronarcosis, rectified current electronarcosis and chemical anaesthesia (benzocaine hydrochloride) on plasma electrolytes and on the osmotic pressure of the blood of the freshwater bream Oreochromis mossambicus were evaluated.
• 2.2. Plasma Ca²⁺, Na⁺ and K⁺ concentrations and the osmotic pressure of the blood were monitored over a period of 7 days.
• 3.3. The results showed that the different electrolytes respond differently to the different techniques.
• 4.4. Chemical anaesthesia exhibited the least effects on the parameters studied.

     

Ionic dependence and vanadate sensitivity of (Na+, K+)-ATPase isolated from branchial sac of ascidians

• 1.1. Ion dependence and vanadium-induced inhibition on branchial sac ATPase in five species of ascidian Phlebobranchiata (vanadium-accumulating) and Stolidobranchiata (iron-accumulating) were studied.
• 2.2. The ATPase was obtained from the microsomal fraction, which was prepared from each ascidian branchial sac.
• 3.3. The ATPase was dependent on Mg²⁺ and activated by exogenous Na⁺ + K⁺.
• 4.4. Ouabain inhibited the ATPase activity in vitro, 10 μM to 100 μM vanadate, in vitro, suppressed the (Na⁺, K⁺)-ATPase.

     

Electrolyte changes,cell volume regulation and hormonal influences during acclimation of rainbow trout (Salmo gairdnerii) to salt water

• 1.1. Rainbow trout were acclimated to salt water (1.5, 2.0 or 3.0%, which means 40, 60 or 85% concentrated sea-water) and the electrolyte, glucose and cortisol concentrations of the plasma as well as the extra- and intracellular muscle space, the muscle electrolyte concentrations and the ATPase activity were analysed.
• 2.2. Plasma osmolality, Na⁺, Ca²⁺ and Mg²⁺ concentrations of the plasma had a maximum at 24 hr after the start of acclimation when acclimated to 3.0% salt water. Plasma osmolality, Na⁺ and Mg²⁺ concentrations were significantly higher during the whole acclimation time when exposed to 3.0% salt water.
• 3.3. Variations and regulations of ECS and ICS were clearly demonstrated. The intracellular electrolyte concentrations were also maximal at 24 hr.
• 4.4. The plasma glucose level was just slightly elevated, but the cortisol level clearly indicated a stress response at 24 hr.
• 5.5. The activity of gill Na-K-ATPase increased during the acclimation time.
• 6.6. The regulatory processes in trout during acclimation to salt water are compared with those occurring in tilapia and carp.

     

Crayfish retinular cells: Influence of extracellular sodium and calcium upon receptor potential

• 1.1. In crayfish, light stimulation of the retinular cells induces a depolarizing receptor potential.
• 2.2. Experiments were designed to determine the role of Na⁺ and Ca²⁺ on receptor potential during dark And light states.
• 3.3. Depolarization depends on Na⁺ and Ca²⁺ availability to the retinular cell.
• 4.4. Repolarization velocity and response duration depend on extracellular Ca²⁺ availability.
• 5.5. Light adaptation increases receptor potential dependence on calcium and sodium ions.
• 6.6. We analyse these results with respect to other invertebrate photoreceptors.

     

Effects of Na+ and/or K+ on the Mg2+-dependent ATPase activities in shrimp (Macrobrachium amazonicum) gill homogenates

• 1.1. Homogenates of gills from the freshwater shrimp M. amazonicum exhibit the following ATPase activities: (i) a basal, Mg²⁺-dependent ATPase; (ii) an ouabain-sensitive, Na⁺ + K⁺-stimulated ATPase; (iii) an ouabain-insensitive, Na⁺-stimulated ATPase; and (iv) an ouabain-insensitive, K⁺-stimulated ATPase.
• 2.2. K⁺ suppresses the Na⁺-stimulated ATPase activity in a mixed-type kind of inhibition, whereas Na⁺ does not exert any noticeable effect on the K⁺-stimulated ATPase activity.
• 3.3. The Na⁺- and the K⁺-stimulated ATPase activities are totally inhibited by 5 mM ethacrynic acid in the incubation medium.
• 4.4. The Na⁺- and the K⁺-stimulated ATPase activities are not expressions of the activation of a Ca-ATPase.
• 5.5. The possible localization and roles of the described ATPases within the gill epithelium are briefly discussed and evaluated.

     

Bioelectrical potentials across the mantle epithelium of Achatina fulica

• 1.1. The shell side of the mantle of Achatina fulica is several millivolts positive to the blood side in vitro.
• 2.2. The electrical potential does not depend on Na⁺, Ca²⁺, Mg²⁺, K⁺ or HCO₃⁻ but requires the presence of chloride on the shell side.
• 3.3. The potential difference and short-circuit current ranged from 3.0 to 30.0 mV and 15.0 to 75 μA/cm² with averages at 10m V and 50 μA/cm² respectively.
• 4.4. The electrical gradient is reduced by 2,4-dinitrophenol, thiocyanate and furosemide but not by ouabain, CO₂ or acetozolamide.
• 5.5. It is suggested that the nature and mechanism of electrogenesis in Achatina parallels that of the Helix mantle.

     

High-affinity Ca2+-Mg2+-ATPase in kidney of euryhaline Gillichthys mirabilis: kinetics,subcellular distribution and effects of salinity

• 1.1. Two components of Ca²⁺-Mg²⁺-ATPase are observed in kidneys of G. mirabilis. The high-affinity component has a K_0.5Ca of 0.23μM; the low-affinity activity K_0.5Ca is 90–110μM. The high-affinity activity requires Mg²⁺, displays Michaelis-Menten kinetics, has peak activity at 1.2 μM Ca²⁺, and is insensitive to ouabain and Na⁺ azide.
• 2.2. In subcellular fractions, the high-affinity component segregates with Na⁺-K⁺-ATPase and is localized predominantly in BLM. The low-affinity component is broadly distributed among membranous organelles, including brush border, and may be equivalent to alkaline phosphatase.
• 3.3. Specific activity of the high-affinity Ca²⁺-Mg²⁺-ATPase is modestly increased following adaptation of fish to FW, but total renal high-affinity activity is greatest in the hypertrophied kidneys of FW-adapted fish and is least in kidneys of fish adapted to 200% SW.
• 4.4. High-affinity Ca²⁺-Mg²⁺-ATPase may be associated with active Ca²⁺ transport or with regulation of intracellular Ca²⁺ concentration of tubular cells.

     

Behaviour and haemolymphatic ionic composition of the intertidal crab Chasmagnathus granulata dana, 1851 (Crustacea: Decapoda) during emersion

• 1.1. Behavioural observations and haemolymphatic measurements of Na⁺ K⁺ and Ca⁺ were performed in Chasmagnalhus granulata during emersion.
• 2.2. Activity levels were found to be higher during voluntary emersion periods than when the animals were submerged. A lt₅₀ of 39.45 hr was observed when no access to water was allowed.
• 3.3. The Na⁺ and K⁺ and Ca⁺ levels increased during aerial exposure. The Na⁺ and K⁺ levels were restored prior the end of the experimental period. Mechanisms for such regulation are therefore discussed. The Ca²⁺ levels, remaining high during emersion, are probably a result of acid-base balance adjustments.

     

The possibility that Ca2+-ATPase from the plasma membrane-rich fraction of bovine parotid gland is ecto-Ca2+-dependent nucleoside triphosphatase

• 1.1. Parotid plasma membrane nonpump low-affinity Ca²⁺-ATPase, which possesses high-affinity (Ca²⁺ + Mg²⁺ )-ATPase activity, was characterized.
• 2.2. Purified Ca²⁺-ATPase hydrolyzed the nucleoside triphosphates, GTP, ITP, CTP, UTP, TTP (67–93% of ATP) and nucleoside diphosphates, ADP. GDP, IDP, CDP, TDP (12–40% of ATP) but not AMP and p-NPP.
• 3.3. The maximum activities of Ca²⁺- and (Ca²⁺ +Mg²⁺ )-ATPases were obtained in the presence of 1 mM and 0.13 μ M Ca²⁺, respectively.
• 4.4. The K_m values for Ca²⁺ in Ca²⁺- and (Ca²⁺+ Mg²⁺ )-ATPases were 0.2 mM and 22 nM. respectively.
• 5.5. The activities of both Ca²⁺- and (Ca²⁺ + Mg²⁺ )-ATPases were found in the right-side-out-vesicles obtained from the plasma membrane-rich fraction.
• 6.6. These features suggest that Ca²⁺-ATPase is an ecto-Ca²⁺-dependent nucleoside triphosphatase.

     

Salinity-dependence of the properties of gill (Na++K+-ATPase in rainbow trout Oncorhynchus mykiss

• 1.1. The expected higher gill (Na⁺+K⁺)-ATPase activity in rainbow trout adapted to brackish water (BW) with respect to fresh water (FW) is accompanied by some changes in the enzyme kinetics while the enzyme sensitivity to ouabain is unaffected
• 2.2. Maximal activation is attained under the optimal conditions of 4 mM ATP, 7.5 mM Mg²⁺, 50 mM Na⁺, 2.5 mM K⁺, pH 7.0 in FW, and 3 mM ATP, 10 mM Mg²⁺, 100 mM Na⁺, 10 mM K⁺, pH 7.5 in BW.
• 3.3. The change of the enzyme activation kinetics by Mg²⁺, ATP, Na⁺ and K⁺ from simple saturation in FW to cooperativity in BW and other habitat-dependent variations including the pH alkaline shift in BW are hypothetically related to an adaptive significance to the different environmental salinity.
• 4.4. Gill total lipids and phospholipids are 30% lower in BW than in FW while their ratio is constant; some differences in gill total lipid fatty acid composition between FW and BW do not significantly affect the unsaturation parameters.

     

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.

     

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.

     

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.

     

Salinity tolerance of adult and juvenile red king crabs Paralithodes camtschatica

• 1.1. Juvenile king crabs were more tolerant of reduced salinities than adult crab; juvenile crab were better volume regulators at reduced salinities than adult crab.
• 2.2. Adult female king crab hemolymph was hyperosmotic to full seawater (30 ppt) and isosmotic to dilute seawater. Juvenile king crab (2 years old) were hypoosmotic at the same concentrations.
• 3.3. Lower osmotic concentration of juvenile hemolymph is at least partially due to lower sodium concentration.
• 4.4. Juvenile king crab can tolerate some dilution and survive for short periods in the reduced salinity of the lower intertidal zone.

     

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.

     

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.

     

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.

     

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.