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PubMed2003

Bicarbonate surfoxidants: micellar oxidations of aryl sulfides with bicarbonate-activated hydrogen peroxide.

The mechanism and kinetics of bicarbonate-catalyzed oxidations of sulfides by H(2)O(2) at the aqueous /cationic micellar interface have been investigated. The general term surfoxidant is introduced to describe the combination of an ionic surfactant with a reactive counterion that is itself an oxidant or activates an oxidant from the bulk solution to form an oxidant counterion. It is shown that the new catalytic cationic surfoxidant CTAHCO(3) (cetyltrimethylammonium bicarbonate) significantly enhances the overall oxidation rates as compared to the addition of bicarbonate salts to CTACl and CTABr, for which the halide counterions must undergo equilibrium displacement by the oxidant anion (peroxymonocarbonate, HCO(4)(-)). General equations based on the classic pseudophase model have been derived to account for the preequilibrium reaction in the aqueous and micellar phases, and the resulting model can be used to describe any micellar reaction with associated preequilibria. Rate constants and relevant equilibrium constants for HCO(4)(-) oxidations of aryl sulfides at micellar surfaces have been estimated for CTAHCO(3), CTACl, and CTABr. The second-order rate constants in the Stern layer (k(2)(m)) for sulfide oxidations by HCO(4)(-) are estimated to be approximately 50-fold (PhSEtOH) and approximately 180-fold (PhSEt) greater than the background rate constant k(m)(0) for oxidation by H(2)O(2) at the micellar surface. The estimated values of k(2)(m) are lower than the corresponding values in water by a factor of 20-70 depending on the substrate, but the high local concentration of the bicarbonate activator in the surfoxidant and the local accumulation of substrate as a result of strong binding to the micelle lead to a net increase in the observed reaction rates. Comparisons of CTAHCO(3)-activated peroxide to other highly reactive oxidants such as peroxymonosulfate (HSO(5)(-)) in aqueous surfactant media suggest a wide variety of potential applications for this green oxidant.

Journal Article↗
PubMed1999

Sodium bicarbonate and potassium bicarbonate supplements for broilers can cause poor performance at high temperatures.

1. Supplements of between 2 and 8 g of sodium bicarbonate (NaHCO3)/l in drinking water provided between 21 and 49 d of age to broilers at 31 degrees C increased growth after 35 d of age and food intake after 42 d of age compared to unsupplemented controls. The most consistent responses were observed with 2 g NaHCO3/l. 2. Differences in weekly water intakes with different concentrations of NaHCO3 in the drinking water did not equate with variations in weekly food intake and growth. 3. Unexpected high mortality from dehydration and nephrosis was observed with a 10 g NaHCO3/l supplement. This mortality was associated with major changes in blood acid-base balance and plasma electrolyte concentrations. 4. Dietary supplements of NaHCO3 gave significantly better food conversion and numerically better growth in broilers at 31 degrees C than supplements of potassium bicarbonate (KHCO3) providing similar dietary concentrations of bicarbonate. 5. Supplements of NaHCO3 were more toxic to broiler chickens when supplied in the drinking water than in the diet. This appeared to be related to the intake of sodium and alterations to cellular membrane ionic potential.

Animal Feed↗
PubMed1995

Haemodynamic and metabolic effects in diabetic ketoacidosis in rats of treatment with sodium bicarbonate or a mixture of sodium bicarbonate and sodium carbonate.

To examine factors determining the haemodynamic and metabolic responses to treatment of diabetic ketoacidosis with alkali, groups of anaesthetised and ventilated rats with either diabetic ketoacidosis (mean arterial pH 6.86-6.96, mean arterial blood pressure 63-67 mm Hg) or hypovolaemic shock due to blood withdrawal (mean pHa 7.25-7.27, mean arterial blood pressure 36-41 mm Hg) were treated with sodium chloride ('saline'), sodium bicarbonate or 'Carbicarb' (equimolar bicarbonate plus carbonate). In the diabetic ketoacidosis series, treatment with either alkali resulted in deterioration of mean arterial blood pressure and substantial elevation of blood lactate, despite a significant rise in myocardial intracellular pH determined by 31P-magnetic resonance spectroscopy. These effects were accompanied by falling trends in the ratios of myocardial phosphocreatine and ATP to inorganic phosphate. Erythrocyte 2,3-bisphosphoglycerate was virtually absent in animals with diabetic ketoacidosis of this severity and duration. In contrast, in shock due to blood withdrawal, infusion of saline or either alkali was accompanied by a transient elevation of mean arterial blood pressure and no significant change in the already elevated blood lactate; erythrocyte 2,3-bisphosphoglycerate was normal in these animals. The effect of alkalinization in rats with severe diabetic ketoacidosis was consistent with myocardial hypoxia, due to the combination of very low initial erythrocyte 2,3-bisphosphoglycerate, alkali-exacerbated left shift of the haemoglobin-oxygen dissociation curve and artificial ventilation. No evidence was found for any beneficial effect of 'Carbicarb' in either series of animals; 'Carbicarb' and sodium bicarbonate could be deleterious in metabolic acidosis of more than short duration.

3-Hydroxybutyric Acid↗
PubMed1985

Are sodium bicarbonate and potassium bicarbonate fully dissociated under physiological conditions?

In solutions containing 160 mmol/l Na+ and K+, respectively, measurements with an ion-selective electrode system (KNA1, Radiometer), showed apparent falls in the respective Na+ and K+ concentrations when C1- was replaced by HCO3-. After correction for the change in liquid junction potential, the fall was 9.2 mmol/l for Na+ and 7.3 mmol/l for K+. On the basis of these findings we conclude that sodium bicarbonate and potassium bicarbonate are not fully dissociated in solution, and that NaHCO3(0) and KHCO3(0) do exist as chemical components with association constants of 0.72 and 0.55, respectively. Using these association constants, normal plasma will contain 1.2 mmol/l NaHCO3(0) and 0.03 mmol/l KHCO3(0). Thus NaHCO3(0) accounts for virtually the same amount of CO2 as the physically dissolved fraction. A review of all the currently known CO2 species in plasma suggests that there may be a residue of about 2 mmol/l of unknown CO2 species in normal plasma.

Bicarbonates↗
PubMed1988

The absence of bicarbonate-stimulated ATPase activity in the plasma membranes of the bicarbonate secreting ox corneal endothelial cells.

Membranes of ox corneal endothelial cells were studied for their surface area by electron microscopical stereology and then separated from homogenates on self forming Percoll gradients. Enzymic analysis of the plasma membrane-enriched fraction failed to demonstrate an ATPase activity which was stimulated by the presence of bicarbonate ions. It is proposed that the well-established bicarbonate secretion of these cells may be coupled to the plasma membrane (Na+ + K+)-ATPase activity by the stoichiometry of Na+/HCO3- close to 1:1.

Adenosine Triphosphatases↗
PubMed2002

A new rapidly absorbed paracetamol tablet containing sodium bicarbonate. I. A four-way crossover study to compare the concentration-time profile of paracetamol from the new paracetamol/sodium bicarbonate tablet and a conventional paracetamol tablet in fed and fasted volunteers.

The primary objective of this four-way crossover study was to compare the concentration-time profile of paracetamol from a new rapidly absorbed paracetamol tablet containing sodium bicarbonate (PS) with a conventional paracetamol tablet (P), in a panel of 28 fed and fasted healthy volunteers. The results demonstrated that paracetamol was absorbed more rapidly from tablets containing sodium bicarbonate compared to conventional tablets, as indicated by a shorter tmax in both the fed and fasted state and a higher Cmax in the fasted state. The two formulations were bioequivalent with respect to area under curve (AUC). Food did not affect the extent of absorption from either formulation, as indicated by AUC, however, food did reduce the rate of absorption from both formulations, as indicated by a longer tmax and a lower Cmax. Metabolic activation of paracetamol to its oxidation metabolites, as assessed by combined partial clearances to subsequent secondary metabolites cysteine and mercapturic acid conjugates, indicated that the two formulations were bioequivalent in this respect.

Acetaminophen↗
PubMed1996

In vitro effects of bicarbonate and bicarbonate-lactate buffered peritoneal dialysis solutions on mesothelial and neutrophil function.

The inclusion of bicarbonate in the formulation of peritoneal dialysis solutions may avoid the in vitro impairment of certain cell functions seen with acidic lactate-based fluids. The supranormal physiological levels of HCO3- and PCO2 inherent in such formulations may, however, not be biocompatible. This study compared the in vitro biocompatibility of a pH 5.2 lactate-based formulation with formulations containing either 40 mM lactate at pH 7.4, 38 mM HCO3- at pH 6.8 (PCO2 at approximately 240 mm Hg) or 7.4 (PCO2 at approximately 60 mm Hg), and 25 mM HCO3- plus 15 mM lactate at pH 6.8 (PCO2 at approximately 160 mm Hg) or 7.4 (PCO2 at approximately 40 mm Hg). Significant release of lactate dehydrogenase or decreases in ATP content by human peritoneal mesothelial cells (HPMC) and human peripheral polymorphonuclear leukocytes (PMN) after a 30-min exposure to each test solution was only seen with the pH 5.2 lactate-based fluid. The ATP content of HPMC exposed to this fluid returned to control levels after 30 min of recovery in M199 control medium but showed a trend toward decreasing ATP content at 240 min. Similarly, interleukin (IL)-1 beta-induced IL-6 synthesis by HPMC was also only significantly reduced by the pH 5.2 lactate solution. PMN chemiluminescence was unaffected by 30-min exposure to all test solutions except for the pH 5.2 lactate formulation. Staphylococcus epidermidis phagocytosis was reduced to between 46 to 57% of control with all test solutions except the pH 5.2 lactate solution, which further suppressed the chemiluminescence response to 17% of control. These data suggest that short exposure to supranormal physiological levels of HCO3- and PCO2 does not impair HPMC or PMN viability and function. Furthermore, neutral pH lactate-containing solutions show equivalent biocompatibility to bicarbonate-based ones.

Adenosine Triphosphate↗
PubMed2003

Intestinal bicarbonate secretion in marine teleost fish-source of bicarbonate, pH sensitivity, and consequences for whole animal acid-base and calcium homeostasis.

Whole animal studies using seawater European flounder (Platichthys flesus) revealed that increasing intestinal [Ca(2+)] to 20 mM stimulated net HCO(3)(-) base secretion by 57%, but this was effectively balanced by an increase in net acid secretion, likely from the gills, to maintain whole animal acid-base status. Higher Ca(2+) concentrations (40 and 70 mM) in ambient seawater resulted in reduced plasma total CO(2). This indicates (1) imperfect acid-base compensation, and (2) that endogenous metabolic CO(2) is insufficient to fuel intestinal HCO(3)(-) secretion, under hyper-stimulated conditions. Bicarbonate secretion plays an important role in preventing calcium absorption by precipitating a large fraction of the imbibed calcium as CaCO(3). Indeed, under high Ca(2+) conditions (20 mM), up to 75% of the intestinal Ca(2+) is precipitated as CaCO(3) and then excreted. This is undoubtedly important in protecting the marine teleost kidney from the need for excessive calcium excretion and risk of renal stone formation. Using an in vitro pH-stat technique with the isolated intestinal epithelium, the replacement of serosal CO(2) with a HEPES buffered saline had no effect on HCO(3)(-) secretion, indicating that the endogenous supply of HCO(3)(-) from CO(2) hydration within epithelial cells is adequate for driving baseline secretion rates. Further, in vitro data demonstrated a stimulatory effect of low pH on intestinal HCO(3)(-) secretion. Thus, both luminal Ca(2+) and H(+) can regulate HCO(3)(-) secretion but the precise mechanisms and their potential interaction are currently unresolved.

Acid-Base Equilibrium↗
PubMed1978

The metabolism of [14C]bicarbonate by Streptococcus lactis: the fixation of [14C]bicarbonate by pyruvate carboxylase.

The fixation of [14C]bicarbonate into aspartate by Streptococcus lactis C10 was achieved by the combined reactions of pyruvate carboxylase (E.C. 6.4.1.1) and glutamate-oxaloacetate transaminase (E.C. 2.6.1.1). The pyruvate carboxylase from Str. lactis C10, which was most active at pH 8.0, was activated by the divalent metal ions Mn2+, Mg2+ and Co2+, and inhibited by sulphydryl reagents. The enzyme was inhibited non-competitively by aspartic acid and competitively by oxaloacetate.

Adenosine Diphosphate↗
PubMed1989

Proximal bicarbonate absorption independent of Na+-H+ exchange: effect of bicarbonate load.

To study proximal tubule bicarbonate absorption that is not due to the neutral Na+-H+ antiporter, mid to late proximal convolutions of the rat kidney were microperfused in vivo with a sodium-free choline solution containing 10(-3) M amiloride. The average sodium concentration resulting from sodium influx was 12 mM. At such low intraluminal [Na+], 10(-3) M amiloride should have inhibited the Na+-H+ antiporter by greater than 95%. When 25 mM HCO3- was in the perfusion fluid, measured total CO2 absorption was 100 pmol.mm-1.min-1. When luminal [HCO3-] was raised to 50 mM, and blood [HCO3-] was also raised to approximately 50 mM to avoid a transepithelial HCO3- concentration gradient, total CO2 absorption increased to greater than 300 pmol.mm-1.min-1. Thus raising intraluminal HCO3- concentration caused a marked increase in total CO2 absorption even though intraluminal [Na+] was low and amiloride was present. Control perfusions containing 140 mM Na+ yielded total CO2 absorption that was approximately 100 pmol.mm-1.min-1 higher than with the respective sodium-free perfusion solutions. In additional experiments, either DCCD or NEM was added to sodium-free perfusion solutions to inhibit H+-ATPase. These inhibitors reduced Na+-H+ independent total CO2 absorption markedly. Our observations suggest that under physiological acid-base conditions, sodium-independent H+ secretion can account for approximately 50% of total HCO3- absorption in mid to late proximal convolutions. This mechanism is stimulated by an increase in ambient HCO(-3) concentration to a degree that might account for the load-dependency of proximal HCO(-3) absorption in these segments of the proximal tubule.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Distal tubule bicarbonate accumulation in vivo. Effect of flow and transtubular bicarbonate gradients.

We have performed microperfusion studies on distal tubules of normal and alkalotic rats in an attempt to demonstrate in vivo bicarbonate secretion. All perfusion solutions were free of phosphate and other nonbicarbonate buffers. In both normal and alkalotic rats, distal perfusions elicited significant tCO2 entry only at high flow (24 nl/min). Even when perfusate tCO2 concentration closely matched plasma tCO2 concentration (30 mM tCO2), significant tCO2 entry again occurred at high flow. This was associated with a rise of the perfusate tCO2 concentration, which indicated net entry of tCO2 against a concentration gradient. In this "symmetrical" perfusion situation, acetazolamide blockade prevented tCO2 entry. Accordingly: distal tubule tCO2 entry is demonstrable in both alkalotic and normal rats at high flow rates; increasing perfusate tCO2 concentration can suppress tCO2 entry; and entry can occur in the absence of a gradient and this effect can be blocked by acetazolamide.

Acetazolamide↗
PubMed2005

Cobalt(III) carbonate and bicarbonate chelate complexes of tripodal tetraamine ligands containing pyridyl donors: the steric basis for the stability of chelated bicarbonate complexes.

The synthesis and characterization (X-ray crystallography, UV/vis spectroscopy, electrochemistry, ESI-MS, and (1)H, (13)C, and (59)Co NMR) of the complexes [Co(L)(O(2)CO)]ClO(4)xH(2)O (L = tpa (tpa = tris(2-pyridylmethyl)amine) (x = 1), pmea (pmea = bis((2-pyridyl)methyl)-2-((2-pyridyl)ethyl)amine) (x = 0), pmap (pmap = bis(2-(2-pyridyl)ethyl)(2-pyridylmethyl)amine) (x = 0), tepa (tepa = tris(2-(2-pyridyl)ethyl)amine) (x = 0)) which contain tripodal tetradentate pyridyl ligands and chelated carbonate ligands are reported. The complexes display different colors in both the solid state and solution, which can be rationalized in terms of the different ligand fields exerted by the tripodal ligands. Electrochemical data show that [Co(tepa)(O(2)CO)](+) is the easiest of the four complexes to reduce, and the variation in E(red.) values across the series of complexes can also be explained in terms of the different ligand fields exerted by the tripodal ligands, as can the (59)Co NMR data which show a chemical shift range of over 2000 ppm for the four complexes. [Co(pmea)(O(2)CO)](+) is fluxional in aqueous solution, and VT NMR spectroscopy ((1)H and (13)C) in DMF-d(7) (DMF = dimethylformamide) over the temperature range -25.0 to 75.0 degrees C are consistent with inversion of the unique six-membered chelate ring. This process shows a substantial activation barrier (DeltaG(#) = 58 kJ mol(-1)). The crystal structures of [Co(tpa)(O(2)CO)]ClO(4)xH(2)O, [Co(pmea)(O(2)CO)]ClO(4).3H(2)O, [Co(pmap)(O(2)CO)]ClO(4), and [Co(tepa)(O(2)CO)]ClO(4) are reported, and the complexes containing the asymmetric tripodal ligands pmea and pmap both crystallize as the 6-isomer. The carbonate complexes all show remarkable stability in 6 M HCl solution, with [Co(pmap)(O(2)CO)](+) showing essentially no change in its UV/vis spectrum over 4 h in this medium. The chelated bicarbonate complexes [Co(pmea)(O(2)COH)]ZnCl(4), [Co(pmap)(O(2)COH)][Co(pmap)(O(2)CO)](ClO(4))(3), [Co(pmap)(O(2)COH)]ZnCl(4)xH(2)O, and [Co(pmap(O(2)COH)]ZnBr(4)x2H(2)O can be isolated from acidic aqueous solution, and the crystal structure of [Co(pmap)(O(2)COH)]ZnCl(4)x3H(2)O is reported. The stability of the carbonate complexes in acid is explained by analysis of the crystallographic data for these, and other slow to hydrolyze chelated carbonate complexes, which show that the endo (coordinated) oxygen atoms are significantly hindered by atoms on the ancillary ligands, in contrast to complexes such as [Co(L)(O(2)CO)](+) (L = (NH(3))(4), (en)(2), tren, and nta), which undergo rapid acid hydrolysis and which show no such steric hindrance.

Journal Article↗
PubMed1989

Potassium bicarbonate, but not sodium bicarbonate, reduces urinary calcium excretion and improves calcium balance in healthy men.

Previous studies demonstrated that the administration of NaHCO3 or sodium citrate had either only a small effect to reduce urinary Ca excretion or no effect, but that potassium citrate significantly reduced urinary Ca excretion. In order to further evaluate and compare the effects of NaHCO3 and of KHCO3, we performed ten metabolic balances in healthy men during 18 control days, 12 days of NaHCO3, 60 mmol/day and 12 days of KHCO3, 60 mmol/day. Six subjects were fed a low Ca diet (5.2 +/- 0.7 SD mmol/day) and three of these were also given calcitriol (0.5 microgram 6-hourly). Four subjects ate a normal Ca diet (19.5 +/- 1.3 mmol/day). For all 10 subjects, KHCO3 administration reduced urinary Ca excretion from control by -0.9 +/- 0.7 mmol/day, P less than 0.001. Net intestinal Ca absorption did not change detectably so that Ca balances became less negative by a +0.9 +/- 0.9 mmol/day; P = 0.01. KHCO3 administration was also accompanied by more positive PO4 and Mg balances. NaHCO3 administration had no significant effect on urinary Ca excretion or Ca balance. NaHCO3 and KHCO3 administration were accompanied by equivalently more positive Na or K balances, respectively and equivalently more negative acid balances (HCO3 retention). Neither NaHCO3 or KHCO3 altered fasting serum HCO3 concentrations, blood pH, serum 1,25-(OH)2-D or PTH concentrations. We conclude that KHCO3 promotes more positive Ca balances by either enhancing renal Ca retention or skeletal Ca retention or both.

Adult↗
PubMed1994

Bicarbonate transport under nominally bicarbonate-free conditions in bovine corneal endothelium.

Fluid transport by the corneal endothelium is supported in air equilibrated, nominally HCO3- free Ringer's, yet it is inhibited by carbonic anhydrase inhibitors indicating dependence on the presence of CO2. It is possible that the CO2/HCO3- contained in air and/or the CO2 derived from oxidative metabolism is sufficient to support HCO3- transport. This study investigates whether endothelial HCO3- transport mechanisms, Na+:HCO3- cotransport and Cl-/HCO3- exchange, are active in the nominal absence of HCO3-. In cultured bovine corneal endothelial cells the rate of intracellular pH (pHi) recovery following acid loading in air-equilibrated, nominally HCO(3-)-free solutions was slowed 75% by 0.5 mM amiloride (inhibitor of Na+/H+ exchange), yet 60% of the acid load was still pumped out. This residual acid efflux (or base influx) was N(+)-dependent, slowed 60 +/- 15% by equilibration of solutions with 100% N2 (to minimize CO2 availability) and totally blocked by pretreatment with 100 microM DIDS, an inhibitor of Na+:HCO3- cotransport. Resting cells were acidified 0.19 +/- 0.01 pH units by addition of 0.5 mM H2DIDS when perfused with air-equilibrated solutions, but only 0.03 +/- 0.02 when perfused with 100% N2 equilibrated solutions. Application of 500 microM acetazolamide (a carbonic anhydrase inhibitor) also acidified resting cells, 0.11 +/- 0.01 pH units, but the acidification was eliminated when cells were perfused with 100% N2-equilibrated solutions, indicating the presence of carbonic anhydrase activity under nominally HCO(3-)-free conditions. Cl-/HCO3- exchange activity was eliminated by 100% N2 perfusion and slowed 29% by acetazolamide.(ABSTRACT TRUNCATED AT 250 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗