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.

     

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.

     

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.

     

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.

     

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.

     

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.

     

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.

     

Na+ regulation and (Na++ K+)ATPase activity in the euryhaline fiddler crab Uca minax (Le conte)

• 1.1. Specific activity and kinetic characteristics of the (Na⁺ + K⁺)ATPase have been investigated in the gill epithelium of the hyper-hypoosmoregulator crab Uca minax.
• 2.2. (Na⁺ +K⁺)ATPase activity is shown to be at least three times higher in the posterior gills.
• 3.3. The kinetic study supports the hypothesis of the existence of two different (Na⁺ + K⁺)ATPases: the enzyme activity in the posterior gills could be involved in the transepithelial transport of Na⁺ while the activity of the anterior gills could be responsible for the intracellular regulation of Na⁺ and K⁺.
• 4.4. Significant and specific changes in (Na⁺ +K⁺)ATPase activity occur upon acclimation to media of various salinities.

     

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.

     

The effect on creatine kinase release of altered conditions in the Ca2+ paradox

• 1.1. Release of creatine kinase (CK) in the Ca²⁺ paradox of the Langendorff-perfused rat heart is dependent on the conditions of Ca²⁺ depletion and Ca²⁺ repletion.
• 2.2. CK release is reduced by raising [Ca²⁺]_o during Ca²⁺ depletion and progressively increased by extending the Ca²⁺ free period from 2 to 5 min.
• 3.3. CK release is reduced by decreasing the electrochemical gradient for Ca²⁺ during Ca²⁺ repletion.
• 4.4. The findings are discussed in the light of current hypotheses for the biochemical mechanisms that underlie the Ca²⁺ paradox.

     

Aluminium and calcium affect the perivitelline fluid in fish eggs

• 1.1. Microelectrodes have been used to measure K⁺ activities and electrical potential differences between the perivitelline fluid (pvf) of the eggs of pike (Esox lucius) and surrounding water in a range of pH, calcium and aluminium concentrations.
• 2.2. Potential differences between pvf and water are decreased by Ca²⁺ (10⁻³ M) while Al³⁺ (18 × 10⁻⁶ M) reverses the polarity of the potential difference.
• 3.3. K⁺ activities in the pvf of eggs in 10⁻⁴M KCl + 10⁻⁵M NaCl are decreased by Ca²⁺(10⁻³ M).
• 4.4. The results are discussed with reference to ion-exchange theory and chorion permeability.

     

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.

     

Ca2+-binding and protein-protein interaction domains of the sea urchin extraembryonic coat protein hyalin

• 1.1. As reported previously (Hopper and Robinson, 1990; Int. J. Biochem. 22, 1165–1170) the sea urchin extraembryonic coat protein hyalin undergoes a Ca²⁺-induced self-association into an insoluble gel (gelation) in the presence of Mg²⁺ and/or NaCl.
• 2.2. A 275 kDa peptide fragment, generated by limited tryptic digestion of hyalin, binds Ca²⁺+ but does not undergo gelation in the presence of Ca²⁺, Mg²⁺ and NaCl.
• 3.3. Comparisons between the capacities of hyalin and the 275 kDa peptide fragment to bind Ca²⁺ indicate that the latter binds 88% less Ca²⁺ than hyalin.
• 4.4. However, the presence of Ca²⁺ alone, at a concentration of 5 mM, protects the 275 kDa peptide fragment from further digestion by trypsin mimicking the effect of this cation in protecting hyalin.
• 5.5. Gel exclusion Chromatographie analyses of the 275 kDa peptide fragment, both in the presence and absence of 5 mM Ca²⁺, indicate that this cation does induce self-association of the fragment.
• 6.6. These results provide information on the organization of the functional domains on hyalin which are required for gel formation.

     

Biphasic action of growth hormone on intestinal amino acid absorption in striped bass hybrids

• 1.1. Weekly injections of bovine growth hormone (bGH) increased the maximal transport rate of both Na⁺-dependent and Na⁺ -independent l-leucine transport with little effect on the affinity constants in the intestine of striped bass hybrids.
• 2.2. The Na⁺-dependent and the Na⁺-independent transport of the non-metabolizable analog cycloleucine was also stimulated by bGH.
• 3.3. The Na⁺ -dependent active transport was stimulated 2 days after the hormone treatment, while the stimulation of the Na⁺-independent diffusional transport was not observed until after 2 weeks of treatment.
• 4.4. Studies of intestinal morphometry and l-leucine transport using brush border membrane vesicles suggested that bGH affects intestinal amino acid absorption initially by increasing the number of transporters per cell.
• 5.5. This phase is followed by a general increase of the intestinal mass after long-term treatment with the hormone.

     

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.

     

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.

     

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.

     

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.