Oxalate transport by the mouse intestine in vitro is not affected by chronic challenges to systemic acid–base homeostasis

The strong ion approach provides a quantitative physicochemical method for describing the mechanism for an acid-base disturbance. The approach requires species-specific values for the total concentration of plasma nonvolatile buffers (Atot) and the effective dissociation constant for plasma nonvolatile buffers ( K a), but these values have not been determined for human plasma. Accordingly, the purpose of this study was to calculate accurate Atot and K a values using data obtained from in vitro strong ion titration and CO2tonometry. The calculated values for Atot (24.1 mmol/l) and K a (1.05 × 10−7) were significantly ( P < 0.05) different from the experimentally determined values for horse plasma and differed from the empirically assumed values for human plasma (Atot = 19.0 meq/l and K a = 3.0 × 10−7). The derivatives of pH with respect to the three independent variables [strong ion difference (SID), Pco 2, and Atot] of the strong ion approach were calculated as follows: [Formula: see text] [Formula: see text], [Formula: see text]where S is solubility of CO2 in plasma. The derivatives provide a useful method for calculating the effect of independent changes in SID+, Pco 2, and Atot on plasma pH. The calculated values for Atot and K a should facilitate application of the strong ion approach to acid-base disturbances in humans.

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Extraction and Fractionation Effects on Antiplasmodial Activity and Phytochemical Composition of Palicourea hoffmannseggiana

Planta Medica International Open ◽

10.1055/a-1375-6456 ◽

2021 ◽

Vol 8 (01) ◽

pp. e34-e42

Author(s):

Leticia Hiromi Ohashi ◽

Douglas Costa Gontijo ◽

Maria Fernanda Alves do Nascimento ◽

Luciano Ferreira Margalho ◽

Geraldo Célio Brandão ◽

...

Keyword(s):

Growth Inhibition ◽

Scale Up ◽

Indole Alkaloid ◽

Ethanol Extract ◽

Parasite Growth ◽

In Vitro Activity ◽

Acid Base ◽

Leaf Extracts ◽

Leaf Powder

AbstractThe present study on Palicourea hoffmannseggiana, which was collected at Marapanim, state of Pará, Brazil, comprises the preparation of different stem and leaf extracts and fractions. Ethanol, hydroethanol, and water extracts were prepared by several methods and evaluated for in vitro activity against resistant Plasmodium falciparum (W2 strain), disclosing a low parasite growth inhibition effect (< 50%). Dereplication by UPLC-DAD-ESI−MS of the leaf ethanol extract showed the presence of two known alkaloids, lyalosidic and strictosidinic acids, along with a sinapoyl ester of lyalosidic acid, with m/z 719.33 [M+H]+, which is possibly a new monoterpene indole alkaloid representative. Sequential liquid-liquid acid-base alkaloid separations from the leaf ethanol extract as well as directly from leaf powder afforded fractions of increased parasite growth inhibition, reaching up to 92.5±0.7%. The most bioactive fractions were shown to contain the β-carboline alkaloids harmane and 4-methyl-β-carboline, along with N-methyl-tryptamine and N-acetyl-tryptamine, while monoterpene indole alkaloids were detected in inactive fractions of these processes. The present results demonstrate that these preliminary fractionation methods can lead to significantly active fractions supporting an adequate scale-up to carrying out the isolation of anti-plasmodial compounds.

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A simplified strong ion model for acid-base equilibria: application to horse plasma

Journal of Applied Physiology ◽

10.1152/jappl.1997.83.1.297 ◽

1997 ◽

Vol 83 (1) ◽

pp. 297-311 ◽

Cited By ~ 117

Author(s):

Peter D. Constable

Keyword(s):

Human Plasma ◽

Practical Method ◽

Published Data ◽

Strong Ion Difference ◽

Weak Acids ◽

Acid Base ◽

Plasma Protein Concentration ◽

Horse Plasma ◽

Hasselbalch Equation

Constable, Peter D. A simplified strong ion model for acid-base equilibria: application to horse plasma. J. Appl. Physiol. 83(1): 297–311, 1997.—The Henderson-Hasselbalch equation and Stewart’s strong ion model are currently used to describe mammalian acid-base equilibria. Anomalies exist when the Henderson-Hasselbalch equation is applied to plasma, whereas the strong ion model does not provide a practical method for determining the total plasma concentration of nonvolatile weak acids ([Atot]) and the effective dissociation constant for plasma weak acids ( K a). A simplified strong ion model, which was developed from the assumption that plasma ions act as strong ions, volatile buffer ions ([Formula: see text]), or nonvolatile buffer ions, indicates that plasma pH is determined by five independent variables:[Formula: see text], strong ion difference, concentration of individual nonvolatile plasma buffers (albumin, globulin, and phosphate), ionic strength, and temperature. The simplified strong ion model conveys on a fundamental level the mechanism for change in acid-base status, explains many of the anomalies when the Henderson-Hasselbalch equation is applied to plasma, is conceptually and algebraically simpler than Stewart’s strong ion model, and provides a practical in vitro method for determining [Atot] and K a of plasma. Application of the simplified strong ion model to CO2-tonometered horse plasma produced values for [Atot] (15.0 ± 3.1 meq/l) and K a(2.22 ± 0.32 × 10−7 eq/l) that were significantly different from the values commonly assumed for human plasma ([Atot] = 20.0 meq/l, K a = 3.0 × 10−7 eq/l). Moreover, application of the experimentally determined values for [Atot] and K a to published data for the horse (known [Formula: see text], strong ion difference, and plasma protein concentration) predicted plasma pH more accurately than the values for [Atot] and K a commonly assumed for human plasma. Species-specific values for [Atot] and K a should be experimentally determined when the simplified strong ion model (or strong ion model) is used to describe acid-base equilibria.

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N-glycosylation critically regulates function of oxalate transporter SLC26A6

AJP Cell Physiology ◽

10.1152/ajpcell.00171.2016 ◽

2016 ◽

Vol 311 (6) ◽

pp. C866-C873 ◽

Cited By ~ 9

Author(s):

R. Brent Thomson ◽

Claire L. Thomson ◽

Peter S. Aronson

Keyword(s):

Plasma Membrane ◽

Intestinal Secretion ◽

Integral Membrane Proteins ◽

Extracellular Loop ◽

Transport Activity ◽

Intact Cells ◽

Functional Studies ◽

And Function ◽

Oxalate Transport

The brush border Cl−-oxalate exchanger SLC26A6 plays an essential role in mediating intestinal secretion of oxalate and is crucial for the maintenance of oxalate homeostasis and the prevention of hyperoxaluria and calcium oxalate nephrolithiasis. Previous in vitro studies have suggested that SLC26A6 is heavily N-glycosylated. N-linked glycosylation is known to critically affect folding, trafficking, and function in a wide variety of integral membrane proteins and could therefore potentially have a critical impact on SLC26A6 function and subsequent oxalate homeostasis. Through a series of enzymatic deglycosylation studies we confirmed that endogenously expressed mouse and human SLC26A6 are indeed glycosylated, that the oligosaccharides are principally attached via N-glycosidic linkage, and that there are tissue-specific differences in glycosylation. In vitro cell culture experiments were then used to elucidate the functional significance of the addition of the carbohydrate moieties. Biotinylation studies of SLC26A6 glycosylation mutants indicated that glycosylation is not essential for cell surface delivery of SLC26A6 but suggested that it may affect the efficacy with which it is trafficked and maintained in the plasma membrane. Functional studies of transfected SLC26A6 demonstrated that glycosylation at two sites in the putative second extracellular loop of SLC26A6 is critically important for chloride-dependent oxalate transport and that enzymatic deglycosylation of SLC26A6 expressed on the plasma membrane of intact cells strongly reduced oxalate transport activity. Taken together, these studies indicated that oxalate transport function of SLC26A6 is critically dependent on glycosylation and that exoglycosidase-mediated deglycosylation of SLC26A6 has the capacity to profoundly modulate SLC26A6 function.

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Effects of acute temperature change, in vivo and in vitro, on the acid–base status of blood from yellowfin tuna (Thunnus albacares)

Canadian Journal of Zoology ◽

10.1139/z92-098 ◽

1992 ◽

Vol 70 (4) ◽

pp. 654-662 ◽

Cited By ~ 11

Author(s):

Richard W. Brill ◽

Peter G. Bushnell ◽

David R. Jones ◽

Manabu Shimizu

Keyword(s):

Ion Exchange ◽

Exchange Rates ◽

Temperature Change ◽

Yellowfin Tuna ◽

Thunnus Albacares ◽

Skipjack Tuna ◽

Acid Base ◽

System Temperature

In most fishes, blood acid–base regulation following a temperature change involves active adjustments of gill ion-exchange rates which take hours or days to complete. Previous studies have shown that isolated blood from skipjack tuna, Katsuwonus pelamis, and albacore, Thunnus alalunga, had rates of pH change with temperature (in the open system) equivalent to those necessary to retain net protein charge in vivo (≈ −0.016 ΔpH∙ °C−1). It was postulated that this is due to protons leaving the hemoglobin combining with plasma bicarbonate [Formula: see text], which is removed as gaseous CO2, and that this ability evolved so that tunas need not adjust gill ion-exchange rates to regulate blood pH appropriately following ambient temperature changes. We reexamined this phenomenon using blood and separated plasma from yellowfin tuna, Thunnus albacares. Unlike previous studies, our CO2 levels (0.5 and 1.5% CO2) span those seen in yellowfin tuna arterial and venous blood. Various bicarbonate concentrations [Formula: see text] were obtained by collecting blood from fully rested as well as vigorously exercised fish. We use our in vitro data to calculate basic physiochemical parameters for yellowfin tuna blood: nonbicarbonate buffering (β), the apparent first dissociation constant of carbonic acid (pKapp), and CO2 solubility (αCO2). We also determined the effects of acute temperature change on arterial pH, [Formula: see text], and partial pressures of O2 and CO2in vivo. The pH shift of yellowfin tuna blood subjected to a closed-system temperature change did not differ from previous studies of other teleosts (≈ −0.016 ΔpH∙ °C−1). The pH shift in blood subjected to open-system temperature change was Pco2 dependent and lower than that in skipjack tuna or albacore blood in vitro, but identical with that seen in yellowfin tuna blood in vivo. However, pH adjustments in vivo were caused by changes in both [Formula: see text] and Pco2. The exact mechanisms responsible for these changes remain to be elucidated.

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Low non-carbonic buffer power amplifies acute respiratory acid-base disorders in septic patients: an in-vitro study

Journal of Applied Physiology ◽

10.1152/japplphysiol.00787.2020 ◽

2021 ◽

Author(s):

Thomas Langer ◽

Serena Brusatori ◽

Eleonora Carlesso ◽

Francesco Zadek ◽

Paolo Brambilla ◽

...

Keyword(s):

Whole Blood ◽

In Vitro Study ◽

Blood Gases ◽

Hemoglobin Concentration ◽

Strong Ion Difference ◽

Strongly Correlated ◽

Acid Base ◽

Buffer Power ◽

Ph Variations

Rationale: Septic patients have typically reduced concentrations of hemoglobin and albumin, the major components of non-carbonic buffer power(β). This could expose patients to high pH variations during acid-base disorders. Objectives: To compare, in-vitro, non-carbonic β of septic patients with that of healthy volunteers, and evaluate its distinct components. Methods: Whole blood and isolated plasma of 18 septic patients and 18 controls were equilibrated with different CO2 mixtures. Blood gases, pH and electrolytes were measured. Non-carbonic β and non-carbonic β due to variations in Strong Ion Difference (βSID) were calculated for whole blood. Non-carbonic β and non-carbonic β normalized for albumin concentrations (βNORM) were calculated for isolated plasma. Representative values at pH=7.40 were compared. Albumin proteoforms were evaluated via two-dimensional electrophoresis. Measurements and Main Results: Hemoglobin and albumin concentrations were significantly lower in septic patients. Septic patients had lower non-carbonic β both of whole blood (22.0±1.9 vs. 31.6±2.1 mmol/L, p<0.01) and plasma (0.5±1.0 vs. 3.7±0.8 mmol/L, p<0.01). Non-carbonic βSID was lower in patients (16.8±1.9 vs. 24.4±1.9 mmol/L, p<0.01) and strongly correlated with hemoglobin concentration (r=0.94, p<0.01). Non-carbonic βNORM was lower in patients (0.01 [-0.01 - 0.04] vs. 0.08 [0.06 - 0.09] mmol/g, p<0.01). Septic patients and controls showed different amounts of albumin proteoforms. Conclusions: Septic patients are exposed to higher pH variations for any given change in CO2 due to lower concentrations of non-carbonic buffers and, possibly, an altered buffering function of albumin. In both septic patients and healthy controls, electrolyte shifts are the major buffering mechanism during respiratory acid-base disorders.

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Influence of training intensity on adaptations in acid/base transport proteins, muscle buffer capacity, and repeated-sprint ability in active men

Journal of Applied Physiology ◽

10.1152/japplphysiol.00630.2016 ◽

2016 ◽

Vol 121 (6) ◽

pp. 1290-1305 ◽

Cited By ~ 15

Author(s):

Cian McGinley ◽

David J. Bishop

Keyword(s):

Lactate Threshold ◽

Buffer Capacity ◽

Transport Protein ◽

Confidence Limits ◽

Training Intensity ◽

Acid Base ◽

Repeated Sprint Ability ◽

Repeated Sprint ◽

Sprint Ability

McGinley C, Bishop DJ. Influence of training intensity on adaptations in acid/base transport proteins, muscle buffer capacity, and repeated-sprint ability in active men. J Appl Physiol 121: 1290–1305, 2016. First published October 14, 2016; doi: 10.1152/japplphysiol.00630.2016 .—This study measured the adaptive response to exercise training for each of the acid-base transport protein families, including providing isoform-specific evidence for the monocarboxylate transporter (MCT)1/4 chaperone protein basigin and for the electrogenic sodium-bicarbonate cotransporter (NBCe)1. We investigated whether 4 wk of work-matched, high-intensity interval training (HIIT), performed either just above the lactate threshold (HIITΔ20; n = 8), or close to peak aerobic power (HIITΔ90; n = 8), influenced adaptations in acid-base transport protein abundance, nonbicarbonate muscle buffer capacity (βmin vitro), and exercise capacity in active men. Training intensity did not discriminate between adaptations for most proteins measured, with abundance of MCT1, sodium/hydrogen exchanger (NHE) 1, NBCe1, carbonic anhydrase (CA) II, and CAXIV increasing after 4 wk, whereas there was little change in CAIII and CAIV abundance. βmin vitro also did not change. However, MCT4 protein content only increased for HIITΔ20 [effect size (ES): 1.06, 90% confidence limits × / ÷ 0.77], whereas basigin protein content only increased for HIITΔ90 (ES: 1.49, × / ÷ 1.42). Repeated-sprint ability (5 × 6-s sprints; 24 s passive rest) improved similarly for both groups. Power at the lactate threshold only improved for HIITΔ20 (ES: 0.49; 90% confidence limits ± 0.38), whereas peak O2 uptake did not change for either group. Detraining was characterized by the loss of adaptations for all of the proteins measured and for repeated-sprint ability 6 wk after removing the stimulus of HIIT. In conclusion, 4 wk of HIIT induced improvements in each of the acid-base transport protein families, but, remarkably, a 40% difference in training intensity did not discriminate between most adaptations.

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Regulation of urea synthesis by acid-base balance in vivo: role of NH3 concentration

AJP Renal Physiology ◽

10.1152/ajprenal.1987.252.2.f221 ◽

1987 ◽

Vol 252 (2) ◽

pp. F221-F225 ◽

Cited By ~ 1

Author(s):

S. Cheema-Dhadli ◽

R. L. Jungas ◽

M. L. Halperin

Keyword(s):

Ammonium Concentration ◽

Urea Synthesis ◽

Carbamoyl Phosphate ◽

Acid Base Balance ◽

Acid Base ◽

Fixed Rate ◽

Rate Limiting Step ◽

Base Balance

The purpose of this study was to clarify how changes in acid-base balance influence the rate of urea synthesis in vivo. Since ureagenesis was increased by an ammonium infusion into rats, regulation seemed to be a function of the blood ammonium concentration. The rate of urea synthesis was constant at a fixed rate of ammonium infusion and independent of the conjugate base infused, chloride or bicarbonate. The steady-state blood ammonium concentration was higher in the rats that developed metabolic acidosis. Thus it appeared that regulation was not directly mediated by this ammonium concentration per se. The rate of urea synthesis was also independent of the blood pH. Accordingly, the rate of urea synthesis was examined as a function of the plasma NH3 concentration. The rate of ureagenesis was found to be directly proportional to the plasma NH3 concentration. Assuming that plasma NH3 levels reflect those in mitochondria, the NH3 concentration yielding half-maximal rates of urea synthesis (close to 2 microM) was in the same range as Km for the rate-limiting step in ureagenesis, carbamoyl phosphate synthetase (EC 6.3.4.16). These results suggest that, at a constant ammonium concentration, the decreased rate of ureagenesis caused by a pH fall in vitro could reflect an acidosis-induced decline in the concentration of true substrate (NH3) for this pathway.

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The influence of respiratory acid-base changes on muscle performance and excitability of the sarcolemma during strenuous intermittent hand grip exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.00869.2010 ◽

2012 ◽

Vol 112 (4) ◽

pp. 571-579 ◽

Cited By ~ 7

Author(s):

M. Hilbert ◽

V. Shushakov ◽

N. Maassen

Keyword(s):

Force Production ◽

Respiratory Acidosis ◽

Respiratory Alkalosis ◽

Muscle Performance ◽

Protective Effects ◽

Acid Base ◽

M Wave ◽

Hand Grip

Acidification has been reported to provide protective effects on force production in vitro. Thus, in this study, we tested if respiratory acid-base changes influence muscle function and excitability in vivo. Nine subjects performed strenuous, intermittent hand grip exercises (10 cycles of 15 s of work/45 s of rest) under respiratory acidosis by CO2 rebreathing, alkalosis by hyperventilation, or control. The Pco2, pH, K+ concentration ([K+]), and Na+ concentration were measured in venous and arterialized blood. Compound action potentials (M-wave) were elicited to examine the excitability of the sarcolemma. The surface electromyogram (EMG) was recorded to estimate the central drive to the muscle. The lowest venous pH during the exercise period was 7.24 ± 0.03 in controls, 7.31 ± 0.05 with alkalosis, and 7.17 ± 0.04 with acidosis ( P < 0.001). The venous [K+] rose to similar maximum values in all conditions (6.2 ± 0.8 mmol/l). The acidification reduced the decline in contraction speed ( P < 0.001) but decreased the M-wave area to 73.4 ± 19.8% ( P < 0.001) of the initial value. After the first exercise cycle, the M-wave area was smaller with acidosis than with alkalosis, and, after the second cycle, it was smaller with acidosis than with the control condition ( P < 0.001). The duration of the M-wave was not affected. Acidification diminished the reduction in performance, although the M-wave area during exercise was decreased. Respiratory alkalosis stabilized the M-wave area without influencing performance. Thus, we did not find a direct link between performance and alteration of excitability of the sarcolemma due to changes in pH in vivo.

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