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PubMed1977

Active hydrogen excretion and sodium absorption through isolated frog skin.

The in vitro skin of Rana esculenta was studied in open-circuit conditions. It was shown that when the external face is bathed in a 2-meq solution of NaCl, sodium is absorbed at a significantly higher rate than chloride. The ionic balance is maintained by excretion of hydrogen. With a mucosal solution of 2 meq Na2SO4 the equation relating sodium absorption to proton excretion is JnH+ = (-25 +/- 7) - (0.73 +/- 0.04) JnNa+. The correlation between the two variables is highly significant. Hydrogen excretion obeys saturation kinetics in relation to the sodium concentration of the mucosal solution. Maximum excretion occurs at a sodium concentration of 4 meq. When the mucosal solution is a 115-meq solution of Na2SO4 the net flux of sodium is 2.3 times higher than that of hydrogen. The balance is maintained by absorption of SO42-. The effects of various substances on the Na+ext/H+int exchange were studied. With a mucosal solution of 2 meq Na2SO4 and short-circuit conditions it was shown that the hydrogen excretion is active and nearly the same as in open circuit, the short-circuit current is equal (to within 8%) to the sum of the sodium and hydrogen net fluxes, and the correlation between the movements of the two ions is low. A model relating the active proton excretion with the sodium transport mechanism is proposed.

Acetazolamide↗
PubMed2004

Effects of enteral and intravenous fluid therapy, magnesium sulfate, and sodium sulfate on colonic contents and feces in horses.

OBJECTIVE: To assess changes in systemic hydration, concentrations of electrolytes in plasma, hydration of colonic contents and feces, and gastrointestinal transit in horses treated with IV fluid therapy or enteral administration of magnesium sulfate (MgSO4), sodium sulfate (NaSO4), water, or a balanced electrolyte solution. ANIMALS: 7 horses with fistulas in the right dorsal colon (RDC). PROCEDURE: In a crossover design, horses alternately received 1 of 6 treatments: no treatment (control); IV fluid therapy with lactated Ringer's solution; or enteral administration of MgSO4, Na2SO4, water, or a balanced electrolyte solution via nasogastric intubation. Physical examinations were performed and samples of blood, RDC contents, and feces were collected every 6 hours during the 48 hour-observation period. Horses were muzzled for the initial 24 hours but had access to water ad libitum. Horses had access to hay, salt, and water ad libitum for the last 24 hours. RESULTS: Enteral administration of a balanced electrolyte solution and Na2SO4 were the best treatments for promoting hydration of RDC contents, followed by water. Sodium sulfate was the best treatment for promoting fecal hydration, followed by MgSO4 and the balanced electrolyte solution. Sodium sulfate caused hypocalcemia and hypernatremia, and water caused hyponatremia. CONCLUSIONS AND CLINICAL RELEVANCE: Enteral administration of a balanced electrolyte solution promoted hydration of RDC contents and may be useful in horses with large colon impactions. Enteral administration of either Na2SO4 or water may promote hydration of RDC contents but can cause severe electrolyte imbalances.

Analysis of Variance↗
PubMed2003

The effect of vitamin E supplementation on discoloration of injection-site lesions in retail cuts and the greening reaction observed in injection-site lesions in muscles of the chuck.

Concern has been raised about green discoloration of injection-site lesions in chuck muscles in modified-atmosphere packages. Objectives were: 1) to recreate green lesions, 2) to compare the severity of discoloration of injection-site lesions in chucks from carcasses of control or vitamin E-supplemented steers, and 3) to identify pigment(s) responsible for discoloration via in vitro color reactions. In Exp. 1, 23 steers (BW = 415 kg; 37 d before harvest) were injected with one of 12 pharmaceuticals, following label directions for route and dose, with the exception of a 5-mL maximum dose, to identify a product that could result in discoloration. Two vaccines (Products A and B) resulted in greening. In Exp. 2, 50 steers were injected (i.m.) with Product A and assigned to the control or vitamin E (1,000 IU/steer daily for 60 d) group. After retail display, 80 and 72% of steaks from the control and treatment groups, respectively, were discolored. Although vitamin E did not reduce (P = 0.53) greening, there was a trend (P = 0.10) toward delay discoloration of lesions from the treatment group. In Phase I of Exp. 3, pigments extracted from green lesions obtained from Exp. 2 were compared with solutions, exposed to a high partial pressure of oxygen (ppO), of myoglobin (Mb), copper sulfate, hydrogen peroxide (H2O2), vaccine, and aluminum hydroxide either alone or in combination. In Phase II of Exp. 3, solutions of two or more of Mb, Cu, sodium sulfide, sodium sulfite, sodium sulfate (Na2SO4), and H2O2 were made at pH 7.2 or 5.5 and exposed to low or high ppO. Normal muscle tissue displayed a 3.2 and 56.7% decrease in absorbance/microg of protein as wavelength changed from 654 to 656 nm and 656 to 658 nm, respectively. Pigments from control and treatment group green tissue displayed a 164.5 and 621.3% increase, respectively, in absorbance/microg of protein as wavelength changed from 654 to 656 nm. As wavelength changed from 656 to 658 nm, the absorbance/microg of protein for control and treatment group lesions decreased by 75 and 109%, respectively. The Mb+Cu+Na2SO4 solution, at pH 5.5 and high ppO, exhibited similar absorbance trends as green lesions indicating that greening may result from a Mb, Cu, and Na2SO4 interaction. Results indicated that greening varies with pharmaceuticals and oxidation of tissue cannot be controlled with vitamin E supplementation. Research on the causative agents of green discoloration, with an emphasis on compounds containing sulfate or Cu, is needed.

Animals↗
PubMed1976

Suppressive role of indole on 2-acetylaminofluorene hepatotoxicity.

Indole is known to suppress the hepatotoxicity and carcinogenicity of 2-acetylaminofluorene (AAF) in rats and hamsters. For elucidation of the mechanism of its protective role, 2 experiments were conducted using young male rats. In the 1st experiment, the 24-hr biliary excretion of N-hydroxy-2-acetylaminofluorene (N-OH-AAF)-glucuronide was measured after 2 and 4 weeks of dietary administration of 0.03% AAF with or without 1.6% indole. The amount of [9-14C]N-OH-AAF that was excreted as the glucuronide following a single i.p. injection of [9-14C]AAF was lower after 2 weeks in animals fed AAF and indole, as compared to those fed AAF alone [1.5 +/- 1.2% versus 19.6 +/- 3.6% S.E. (p less than 0.001)]. After 4 weeks of AAF administration without indole, the biliary excretion fell to 4.8 +/- 2.1%. This was also significantly higher than that of the animals fed both AAF and indole [1.8 +/- 1.2% (p less than 0.025)]. The suppressive role of indole on the conjugate excretion was also reflected in a decreased biliary excretion of all [9-14C]AAF metabolites in animals treated with indole alone. In the 2nd experiment, the protective action of indole was assessed by survival following daily i.p. injections of N-OH-AAF and Na2SO4 solution. Na2SO4 increased the hepatotoxicity of N-OH-AAF. Indole suppressed the toxicity of N-OH-AAF even in the presence of Na2SO4. This protective role of indole was partially overcome only when excess sulfate was coadministered. These results indicate that indole suppresses the biliary excretion of the O-glucuronide of N-OHAAF during the initial exposure of the animal to the carcinogen, possibly reflecting decreased N-OH-AAF formation. Indole also modifies the metabolism of AAF FOLLOWING N-hydroxylation, perhaps activating N-OH-AAF, depending upon the concentration of sulfate available.

2-Acetylaminofluorene↗
PubMed2001

[Relations of electrolytes to the by-product CHCl3 produced in electrochemical disinfection].

OBJECTIVE: To investigate the relation of electrolytes(NaCl, Na2SO4) to the by-product CHCl3 produced in the electrochemical disinfection process. METHODS: Taking filtering water, we used the graphite and Ti (matrix)-Ti as electrodes, adjusted the current sample for analysis in different time, and determined the production of CHCl3 under different conditions. RESULTS: Na2SO4 had no effect on the production of CHCl3 in the electrolysis(P > 0.05). but NaCl had the effect and the higher the concentration of Cl- was, the more the production of CHCl3 increased. The production of CHCl3 increased with the length of electrolysis time, and it exceeded the national standard after 10 minutes' electrolysis using Ti (matrix)-Ti as electrodes. When graphite was used as electrodes, the production of CHCl3 was much less. CONCLUSION: Na2SO4 has no effect on the production of CHCl3. Our suggestion is that graphite should be used as the electrodes for electrochemical disinfection of drinking water.

Chloroform↗
PubMed1982

[Subunit interactions in luciferase from the firefly Luciola mingrelica. Their role in the manifestation of enzyme activity and during thermoinactivation].

It was shown that the dimers of the firefly luciferase possess the catalytic activity, whereas the monomers do not. The dissociation constant (Kd) for active dimers was determined at pH 7.0--8.4 within the temperature range of 15--35 degrees and at MgSO4 and Na2SO4 concentrations varying from 37 to 370 mM and 49 to 490 mM, respectively. Under variable conditions the Kd value changed only insignificantly and made up to 13 nm. The substitution of Na2SO4 for MgSO4 decreased Kd 2.5 times. The effective rate constant for the enzyme inactivation (kin) was increased more than 5-fold, when the luciferase concentration was decreased from 200 down to 3.5 nM in the presence of 37 mM MgSO4. When the concentration of the latter was increased up to 185 mM, the value of kin ceased to depend on the enzyme concentration. The decrease of kin was also observed at an increase in Na2SO4. An inactivation pattern for the enzyme in solution was determined both for the monomer and for the dimer of the enzyme. The equations allowing to calculate the inactivation constant for the monomer (Ki) and dimer (k2) at different pH values, temperatures and salt concentrations were obtained. The enzyme was found to be stabilized by salts more than 10-fold, the stabilizing effect being far more pronounced for the enzyme monomer than for the dimer. The dependence of the effective kin value on pH and temperature was primarily influenced by the dependence of the inactivation rate constant for the dimer.

Animals↗
PubMed1997

Response of some Calvin cycle enzymes subjected to salinity shock in vitro.

Leaf enzyme extracts of 10 day old seedlings of horsegram were subjected to NaCl or Na2SO4 treatment in vitro. Salinity shock caused decline in the activities of RuBP carboxylase, R-5-P kinase, R-5-P isomerase and NADP-Gly-3-P dehydrogenase. At low concentrations, Na2SO4 did not alter the activities of R-5-P kinase, R-5-P isomerase and NADP-Gly-3-P dehydrogenase. RuBP carboxylase was found to be more sensitive to salt shock than the other enzymes studied. Further, NaCl was more toxic to the enzyme activities as compared to Na2SO4.

Osmotic Pressure↗
PubMed2025

Untargeted metabolomics reveals anion and organ-specific metabolic responses of salinity tolerance in willow.

Willows can alleviate soil salinisation while generating sustainable feedstock for biorefinery, yet the metabolomic adaptations underlying their tolerance remain poorly understood. Salix miyabeana was treated with two environmentally abundant salts, NaCl and Na2SO4, in a 12-week pot trial. Willows tolerated salts across all treatments (up to 9.1 dS m-1 soil ECe), maintaining biomass while selectively partitioning ions, confining Na+ to roots and accumulating Cl- andin the canopy and adapting to osmotic stress via reduced stomatal conductance. Untargeted metabolomics captured >5000 putative compounds, including 278 core willow metabolome compounds constitutively produced across organs. Across all treatments, salinity drove widespread metabolic reprogramming, altering 28% of the overall metabolome, with organ-tailored strategies. Comparing salt forms at equimolar sodium, shared differentially abundant metabolites were limited to 3% of the metabolome, representing the generalised salinity response, predominantly in roots. Anion-specific metabolomic responses were extensive. NaCl reduced carbohydrates and tricarboxylic acid cycle intermediates, suggesting potential carbon and energy resource pressure, and accumulated root structuring compounds, antioxidant flavonoids, and fatty acids. Na2SO4 salinity triggered accumulation of sulphur-containing larger peptides, suggesting excess sulphate incorporation leverages ion toxicity to produce specialised salt-tolerance-associated metabolites. This high-depth picture of the willow metabolome underscores the importance of capturing plant adaptations to salt stress at organ scale and considering ion-specific contributions to soil salinity.

Salix↗
PubMed2004

Chemical and environmental implications of visible and near-infrared spectral features of salt crusts formed from different brines.

This work describes a laboratory experiment intended to study the formation and spectral reflectance properties of stratified salt crusts that cause severe environmental degradations to soil and water resources in arid regions. Salt crusts were prepared by evaporating three types of saline solutions consisting of i) NaCl - Na2SO4, ii) Na2SO4 - MgSO4, and iii) NaCl - MgSO4 at an initial concentrations of 50 mmol L(-1). They were examined for evaporite mineralogy using X-ray diffraction, optical and reflected microscopes, and for spectral reflectance with a high-resolution spectroradiometer (GER 3700) in the visible and near-infrared regions (400-2500 nm). The study documented chemical and environmental implications of the spectral properties of salt formed from the studied saline-systems. The reported results can be used to understand remotely sensed signatures of salt crusts and their implications.

Desert Climate↗
PubMed1990

Subtypes of excitatory amino acid receptors involved in the stimulation of [3H]dopamine release from cell cultures of rat ventral mesencephalon.

N-methyl-D-aspartic acid (NMDA), quisqualic acid (QUIS), and kainic acid (KAIN), respective agonists for three excitatory amino acid (EAA) receptor subtypes, stimulated [3H]dopamine ([3H]DA) release from dissociated cell cultures of fetal rat ventral mesencephalon. Release evoked by all three agonists was Ca2(+)-dependent and inhibited by broad-spectrum antagonists (D,L-cis-2,3-piperidine dicarboxylic acid [PDA] and kynurenic acid [KYN]). However, both of these antagonists were more potent against KAIN than against QUIS and only KAIN-evoked release was blocked by gamma-D-glutamyl-aminomethyl sulfonic acid (GAMS, IC50 700 microM). NMDA-stimulated [3H]DA release was selectively inhibited by competitive (3-[2-carboxypiperazine-4-yl]propyl-1-phosphonic acid [CPP] and D,L-2-amino-5-phosphonovaleric acid [APV]) and non-competitive (phencyclidine and MK-801) NMDA receptor antagonists. In 1.2 mM Mg2+, NMDA-stimulated [3H]DA release was Na(+)-dependent and inhibited by tetrodotoxin (TTX, 2 microM) or by the local anaesthetic, lidocaine (200 microM). However, in 0 Mg 2+, NMDA-evoked release was not inhibited by TTX or lidocaine. Thus, TTX-sensitivity of the NMDA response in 1.2 mM Mg2+ apparently occurs because Na(+)-action potentials are required to alleviate a Mg2+ blockade. Neither QUIS- nor KAIN-evoked release was affected by Mg2+ or TTX. When extracellular NaCl was replaced by sucrose or Na2SO4, the QUIS response was increased. KAIN-evoked release was unaffected by the sucrose substitution and was attenuated in the Na2SO4-containing buffer. It is concluded that NMDA and QUIS/KAIN release [3H]DA via separate receptor subtypes.

Animals↗
PubMed1996

An enzymatic procedure for the preparation and purification of 3'-phosphoadenosine 5'-phospho-[35S]sulfate ([35S]PAPS): applications in syntheses of 8-azido and 8-bromo derivatives of [35S]PAPS.

This paper describes a rapid and an efficient procedure for the enzymatic synthesis of 3'-phosphoadenosine 5'-phospho[35S]sulfate ([35S]PAPS). [35S]PAPS was synthesized by incubating ATP and a carrier-free [35S]-Na2(35)SO4 with ATP sulfurylase, a recombinant APS kinase and inorganic pyrophosphatase. The transfer of 35SO4 group from [35S]Na2SO4 to [35S]PAPS proceeded more efficiently in the presence of an ATP-regenerating system composed of pyruvate kinase and phosphoenol pyruvate. About 90% of the radioactivity present in the starting material [35S]Na2SO4 was transferred to [35S]PAPS within a 2-h reaction incubation. The reaction products were applied to a Mono Q column, and [35S]PAPS was eluted by a step-wise gradient of triethylamine bicarbonate buffer (pH 7.5). Under these conditions, [35S]PAPS eluted as a sharp peak at 0.7 M triethylammonium bicarbonate and it was very well separated from other contaminants. The purified [35S]PAPS (yield 85%, purity > 95%) was functional in donating sulfate to an oligosaccharide acceptor in a standard sulfotransferase reaction. The enzymatic procedure described above was particularly useful for the synthesis of [35S]PAPS at a wide range of concentrations and specific activities (up to 1500 Ci/mmol). This generally useful approach was also found to be successful in the syntheses of 8-azido and 8-bromo derivatives of [35S]PAPS. Applications of these two derivatives of PAPS, for purification and identification of sulfotransferases, have also been discussed.

Adenosine Triphosphate↗
PubMed1996

The Effects of Salts on the Lower Consolute Boundary of a Nonionic Micellar Solution

A molecular model based in statistical thermodynamics is used to study salt effects on the lower consolute boundary of the aqueous non-ionic surfactant C8E5. The C8E5 micelles are modeled as hard spheres interacting via a temperature-dependent Yukawa attraction and the salt ions are modeled as positively and negatively charged hard spheres interacting via a Coulombic potential. The excess thermodynamic properties due to the Coulombic and Yukawa potentials are evaluated using the analytical solutions to the Ornstein-Zernike equation obtained for the mean spherical approximation closure. The Yukawa parameters for the micelle-micelle attractions are determined by fitting the theoretical phase diagram for a pure Yukawa fluid to the experimental lower consolute boundary for a salt-free C8E5 micelle-water solution. Ion-solvent interactions are indirectly accounted for by using previously determined adjusted values for the cation size and the dielectric constant of the medium. We evaluate theoretical coexistence curves for the C8E5 micelle-salt-water mixtures in the temperature-micelle volume fraction and temperature-salt molarity planes. We calculate the changes in the lower critical solution temperature (LCST) for the C8E5 micelle-salt-water mixture as a function of salt concentration for the salts NaF, NaCl, NaBr, NaI, and Na2SO4 and compare the trends seen with experiments. When ion-solvent interactions are indirectly accounted for, the theory correctly predicts the salting-out trends exhibited by NaF, NaCl, and NaBr. For the 1:2 salt (Na2SO4), charge effects resulting from the higher charge on the ions play a more important role in salting-out than ion-solvent interactions do. The theory, however, cannot predict the salting-in phenomena exhibited by NaI, thus indicating that salting-in is the result of variations in the intermicellar attraction as a function of the salt type and salt concentration. The theoretical results also indicate that excluded-volume forces resulting from the different sizes of the salt ions cannot alone account for the salting-in and salting-out phenomena seen in aqueous nonionic micellar solutions.

Journal Article↗
PubMed1999

Rapid folding with and without populated intermediates in the homologous four-helix proteins Im7 and Im9.

The kinetics and thermodynamics of the folding of the homologous four-helix proteins Im7 and Im9 have been characterised at pH 7.0 and 10 degrees C. These proteins are 60 % identical in sequence and have the same three-dimensional structure, yet appear to fold by different kinetic mechanisms. The logarithm of the folding and unfolding rates of Im9 change linearly as a function of urea concentration and fit well to an equation describing a two-state mechanism (with a folding rate of 1500 s-1, an unfolding rate of 0. 01 s-1, and a highly compact transition state that has approximately 95 % of the native surface area buried). By contrast, there is clear evidence for the population of an intermediate during the refolding of Im7, as indicated by a change in the urea dependence of the folding rate and the presence of a significant burst phase amplitude in the refolding kinetics. Under stabilising conditions (0.25 M Na2SO4, pH 7.0 and 10 degrees C) the folding of Im9 remains two-state, whilst under similar conditions (0.4 M Na2SO4, pH 7.0 and 10 degrees C) the intermediate populated during Im7 refolding is significantly stabilised (KUI=125). Equilibrium denaturation experiments, under the conditions used in the kinetic measurements, show that Im7 is significantly less stable than Im9 (DeltaDeltaG 9.3 kJ/mol) and the DeltaG and m values determined accord with those obtained from the fit to the kinetic data. The results show, therefore, that the population of an intermediate in the refolding of the immunity protein structure is defined by the precise amino acid sequence rather than the global stability of the protein. We discuss the possibility that the intermediate of Im7 is populated due to differences in helix propensity in Im7 and Im9 and the relevance of these data to the folding of helical proteins in general.

Amino Acid Sequence↗
PubMed1985

Active chloride transport in rabbit thick ascending limb of Henle's loop and elasmobranch rectal gland: chloride fluxes in isolated plasma membranes.

To investigate directly whether a sodium-potassium-chloride cotransport system is operating in the mammalian thick ascending limb of Henle's loop (TALH) and in the elasmobranch rectal gland, plasma membrane vesicles were prepared from TALH cells isolated from rabbit kidney outer medulla and from rectal glands of Squalus acanthias, and chloride uptake was measured by a rapid filtration technique. Chloride uptake into TALH vesicles in the presence of a 25 mM Na2SO4, 25 mM K2SO4 gradient reached 70% of equilibrium at 2.5 min. In the presence of both sodium and potassium, the 15 s chloride uptake was inhibited 35% by 1 mM bumetanide. When either sodium or potassium was removed from the incubation medium, chloride uptake decreased to the level observed in the presence of 1 mM bumetanide, 0.5 mM SITS had no effect on chloride uptake by the plasma membrane vesicles. This sodium and potassium dependent, bumetanide sensitive chloride uptake was also observed under tracer exchange conditions. Chloride uptake into rectal gland plasma membrane vesicles in the presence of a 50 mM Na2SO4, 50 mM K2SO4 gradient reached 80% of equilibrium at 2.5 min. 1 mM bumetanide inhibited the 15 s uptake of chloride by 34% and removal of either sodium or potassium from the incubation medium reduced chloride uptake to the level observed in the presence of bumetanide under both gradient and tracer exchange conditions. These studies provide additional support for the hypothesis that a sodium-potassium-chloride cotransport system is operating in these epithelia.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1996

Chloride currents in skeletal muscles of Bufo arenarum.

C1- currents (ICl) were measured in short fibers (1-2 mm) from the lumbricalis muscle of toads (Bufo arenarum) with two microelectrodes (15 degrees C). Initially the fibers were equilibrated in a high (K+)-containing solution: (mM) K2SO4 68; Na2SO4 20; KCl 60; CaSO4 8; MgSO4 1; HEPES 2.5. Constant pulses were applied when all the external K+ was replaced by Cs+: Cs2SO4 68; Na2SO4 20; CsCl 60; CaSO4 8; HEPES 2.5 (pH 7.5). Under these conditions about 80-90% of the current is carried by Cl-. The current-voltage relation is almost linear implying constant conductance and hence voltage-independent permeability. The voltage dependence of the net C1- current could be fitted by constant field equation with a PCl of 3.3 x 10-6 cm/sec. In a separate group of experiments a two-pulse technique was used to estimate the availability and the inactivation of the initial ICl during a test pulse. After returning the potential to the holding potential for various times, test pulses of the same amplitude and duration of the prepulses were applied. The initial current during the test pulse was 70% of the initial current during the prepulse and the recovery was complete in less than 300 msec with a linear relationship between the current during the test pulse and the amplitude of the preceding prepulse. When the test pulses were preceded by a positive prepulse, the initial current for any given test pulse was larger than with a negative prepulse. If we assumed that the initial current during the test pulse is a measure of the number of channels open at the end of the prepulse, these results suggest that hyperpolarizing pulses inactivate and depolarizing prepulses activate the ICl.

Animals↗
PubMed2006

Salt effects on an ion-molecule reaction--hydroxide-catalyzed hydrolysis of benzocaine.

PURPOSE: This work investigates the effect of various salts on the rate of a reaction involving a neutral species (benzocaine alkaline hydrolysis). METHODS: Benzocaine hydrolysis kinetics in NaOH solutions in the presence of different salts were studied at 25 degrees C. Benzocaine solubility in salt solutions was also determined. Solubility data were used to estimate salt effects on benzocaine activity coefficients, and pH was used to estimate salt effects on hydroxide activity coefficients. RESULTS: Salts either increased or decreased benzocaine solubility. For example, solubility increased with 1.0 M tetraethylammonium chloride (TEAC) approximately 3-fold, whereas solubility decreased approximately 35% with 0.33 M Na2SO4. Salt effects on hydrolysis rates were more complex and depended on the relative magnitudes of the salt effects on the activity coefficients of benzocaine, hydroxide ion, and the transition state. As a result, some salts increased the hydrolysis rate constant, whereas others decreased it. For example, the pseudo-first-order rate constant decreased approximately 45% (to 0.0584 h(-1)) with 1 M TEAC, whereas it increased approximately 8% (to 0.116 h(-1)) with 0.33 M Na2SO4. CONCLUSIONS: Different salt effects on degradation kinetics can be demonstrated for a neutral compound reacting with an ion. These salt effects depend on varying effects on activity coefficients of reacting and intermediate species.

Anesthetics, Local↗
PubMed1976

Evidence for electronogenic sodium pumping in the ductal epithelium of rabbit salivary gland and its relationship with (Na+ plus K+)-ATPase.

The temperature dependence of the transepithelial potential difference (PD) of the main duct of the submaxillary gland has been measured during in vitro perfusion studies. The magnitude of the PD depends strongly on the anion composition of the perfusing and bathing fluids. The following combinations of perfusion and bathing fluids respectively were used: (1) Na2SO4/NaCl, (2) Na2SO4, (3) NaCl/-NaCl, (4) NaCl/Na2SO4. The mean transepithelial potential differences at 35 degrees C with these four sets of conditions were respectively: 144, 148, 10 and - 15 mV, serosal side positive with respect to lumen. From the data obtained it was possible to construct Arrhenius plots of temperature dependence of the PD for the four sets of experimental conditions. They all show a breakpoint between 16 and 19 degrees C. The apparent activation energies in the four situations above the breakpoint are 4.2, 1.4, 12.0 and 10.6 kcal/mol, respectively. Below the breakpoint they are 29.9, 37.5, 29.0 and 31.3 kcal/mol, respectively. The rapid change in the PD as a function of temperature (which can also be achieved by the addition of ouabain), the effects of the removal of K+ on the serosal side on the PD, the decrease in the PD after the addition of ouabain or CN-, and the activation energies and breakpoints all lead to the conclusion that a large part of the PD is caused by an electrogenic sodium pump which is very probably the enzyme (Na+ plus K+)-ATPase. When the duct is perfused with Na2SO4 we find, above the breakpoint in the Arrhenius plots, a lower activation energy than is found when perfusing with NaCl.

Adenosine Triphosphatases↗
PubMed1981

Effects of ouabain on frog gastric mucosa in vitro.

The effect of the addition of ouabain to the nutrient solution was determined on resistance, potential difference (p.d.) and H+ secretion rate. In NaCl media, 10(-3) M ouabain decreased significantly the p.d. from 25.6 mV to 16.1 mV in 30 min and to 11.0 mV in 60 min. No significant changes occurred in resistance and H+ secretion rate. In Na2SO4 (Cl(-)-free) media, ouabain produced a biphasic effect on p.d. The p.d. changed from -28.0 mV (nutrient-negative) to a nadir of -37.4 mV in 7 min and then increased to -16.4 mV in 60 min. At the nadir there was no significant change in resistance or H+ secretion rate but at 60 min, unlike Cl- media, resistance increased by 36% and H+ secretion rate decreased by 43%. To decide whether the ouabain-caused decrease in H+ rate in Na2SO4 media was due to an effect on the H+ pump or on resistance of the return pathways, the voltage was clamped at 0 and 40 mV. Clamping the voltage showed that in the case of a marked decrease in the H+ secretion rate, the H+ transport mechanism itself was inhibited (and not the parallel pathway). The decrease in p.d. due to ouabain in Cl- and SO42- media indicates that the (Na+ + K+)-ATPase mechanism may be electrogenic.

Animals↗