Coordination of metabolism and intracellular acid–base status: ionic regulation and metabolic consequences

This review discusses the mechanisms by which animal cells regulate intracellular pH (pHi), the variations in pHi encountered in vivo, and the impact that variations in pHi (and other acid–base variables) have on metabolism. Cells regulate pHi by a combination of (i) physicochemical buffering by intracellular components; (ii) transport of acids and bases across the plasma membrane; and (iii) production and consumption of acids and bases by metabolism. Ionic transport is by far the best studied of these three mechanisms, and several specific plasma membrane exchangers (e.g., Na+–H+ exchange) are important regulators of pHi The precise quantitative contribution of the other two mechanisms to pHi regulation awaits further study. Intracellular pH variations in vivo can be substantial (i.e., up to 1 unit in some cases) and can lead to marked changes in metabolism. Furthermore, changes in carbon dioxide tension and bicarbonate concentration can also affect metabolism. Catecholamines appear to be important regulatory signals in metabolic compensation for acid–base perturbations, but in some cases acid–base disturbances may produce adaptive metabolic changes directly.

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Intracellular pH distribution as a cell health indicator in Saccharomyces cerevisiae

Journal of The Royal Society Interface ◽

10.1098/rsif.2011.0148 ◽

2011 ◽

Vol 8 (64) ◽

pp. 1635-1643 ◽

Cited By ~ 10

Author(s):

Thomas Aabo ◽

Jesper Glückstad ◽

Henrik Siegumfeldt ◽

Nils Arneborg

Keyword(s):

Saccharomyces Cerevisiae ◽

Plasma Membrane ◽

Intracellular Ph ◽

Ph Regulation ◽

Metabolic Enzyme ◽

Transport Mechanisms ◽

Cell Functions ◽

Internal Ph ◽

Ratio Imaging

Internal pH regulation is vital for many cell functions, including transport mechanisms and metabolic enzyme activity. More specifically, transport mechanisms are to a wide degree governed by internal pH distributions. We introduce the term standard deviation of the intracellular pH (s.d.(pH int )) to describe the internal pH distributions. The cellular pH distributional response to external stress such as heat has not previously been determined. In this study, the intracellular pH (pH i ) and the s.d.(pH int ) of Saccharomyces cerevisiae cells exposed to supralethal temperatures were measured using fluorescence ratio imaging microscopy (FRIM). An exponential decline in pH i was observed after an initial small decline. For the first time, we report the use of FRIM for determining in vivo plasma membrane proton permeability coefficients in yeast. Furthermore, the exponential decay of pH i and the rupture of the cell plasma membrane, as measured by propidium iodide staining, at 70°C were not simultaneous but were separated by a significant temporal difference. Finally, a nonlinear relationship between the pH i and s.d.(pH int ) was found; i.e. the s.d.(pH int ) was significantly more sensitive to supralethal temperatures than pH i . s.d.(pH int ) is therefore proposed as an early health/vitality indicator in S. cerevisiae cells exposed to heat stress.

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The effect of acid–base changes on skeletal muscle twitch tension

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y78-087 ◽

1978 ◽

Vol 56 (4) ◽

pp. 543-549 ◽

Cited By ~ 5

Author(s):

David W. Fretthold ◽

Lal C. Garg

Keyword(s):

Carbon Dioxide ◽

Skeletal Muscle ◽

Intracellular Ph ◽

Muscle Tension ◽

Carbon Dioxide Tension ◽

Extracellular Ph ◽

Acid Base ◽

Muscle Twitch ◽

Deficient Diet

The effects of acid–base alterations produced by changing bicarbonate (metabolic type), carbon dioxide tension (respiratory type), or both bicarbonate and carbon dioxide tension (compensated type) on skeletal muscle twitch tension, intracellular pH, and intracellular potassium were studied in vitro. Hemidiaphragm muscles from normal rats and rats fed a potassium-deficient diet were used. Decreasing the extracellular pH by decreasing bicarbonate or increasing CO2 in the bathing fluid produced a decrease in intracellular pH, intracellular K+, and muscle twitch tension. However, at a constant extracellular pH, an increase in CO2 (compensated by an increase in bicarbonate) produced an increase in intracellular K+ and twitch tension in spite of a decrease in intracellular pH. The effect on twitch tension of the hemidiaphragms showed a rapid onset, was reversible, persisted until the buffer composition was changed, and was independent of synaptic transmission.It is concluded that the twitch tension of the skeletal muscle decreases with a decrease in intracellular K+. The muscle tension also decreases with an increase in the ratio of intracellular and extracellular H+ concentration. However, there is no consistent relationship between muscle tension and extracellular or intracellular pH. The muscle tension of the diaphragms taken from K+-deficient rats is more sensitive to variations in CO2, pH, and bicarbonate concentration of the medium than that of the control rat diaphragms.

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Anion channel sensitivity to cytosolic organic acids implicates a central role for oxaloacetate in integrating ion flux with metabolism in stomatal guard cells

Biochemical Journal ◽

10.1042/bj20110845 ◽

2011 ◽

Vol 439 (1) ◽

pp. 161-170 ◽

Cited By ~ 20

Author(s):

Yizhou Wang ◽

Michael R. Blatt

Keyword(s):

Plasma Membrane ◽

Organic Acids ◽

Organic Acid ◽

Stomatal Closure ◽

Anion Channel ◽

Guard Cells ◽

Solute Flux ◽

Stomatal Guard Cells ◽

The Impact

Stomatal guard cells play a key role in gas exchange for photosynthesis and in minimizing transpirational water loss from plants by opening and closing the stomatal pore. The bulk of the osmotic content driving stomatal movements depends on ionic fluxes across both the plasma membrane and tonoplast, the metabolism of organic acids, primarily Mal (malate), and its accumulation and loss. Anion channels at the plasma membrane are thought to comprise a major pathway for Mal efflux during stomatal closure, implicating their key role in linking solute flux with metabolism. Nonetheless, little is known of the regulation of anion channel current (ICl) by cytosolic Mal or its immediate metabolite OAA (oxaloacetate). In the present study, we have examined the impact of Mal, OAA and of the monocarboxylic acid anion acetate in guard cells of Vicia faba L. and report that all three organic acids affect ICl, but with markedly different characteristics and sidedness to their activities. Most prominent was a suppression of ICl by OAA within the physiological range of concentrations found in vivo. These findings indicate a capacity for OAA to co-ordinate organic acid metabolism with ICl through the direct effect of organic acid pool size. The findings of the present study also add perspective to in vivo recordings using acetate-based electrolytes.

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The effect of MEP pathway and other inhibitors on the intracellular localization of a plasma membrane-targeted, isoprenylable GFP reporter protein in tobacco BY-2 cells

F1000Research ◽

10.12688/f1000research.2-170.v2 ◽

2013 ◽

Vol 2 ◽

pp. 170 ◽

Cited By ~ 3

Author(s):

Michael Hartmann ◽

Andrea Hemmerlin ◽

Elisabet Gas-Pascual ◽

Esther Gerber ◽

Denis Tritsch ◽

...

Keyword(s):

Plasma Membrane ◽

Intracellular Localization ◽

Test System ◽

Mep Pathway ◽

Reporter Protein ◽

Visualization System ◽

Gfp Reporter ◽

Carboxy Terminal ◽

The Impact

We have established an in vivo visualization system for the geranylgeranylation of proteins in a stably transformed tobacco BY-2 cell line, based on the expression of a dexamethasone-inducible GFP fused to the carboxy-terminal basic domain of the rice calmodulin CaM61, which naturally bears a CaaL geranylgeranylation motif (GFP-BD-CVIL). By using pathway-specific inhibitors it was demonstrated that inhibition of the methylerythritol phosphate (MEP) pathway with known inhibitors like oxoclomazone and fosmidomycin, as well as inhibition of the protein geranylgeranyltransferase type 1 (PGGT-1), shifted the localization of the GFP-BD-CVIL protein from the membrane to the nucleus. In contrast, the inhibition of the mevalonate (MVA) pathway with mevinolin did not affect the localization. During the present work, this test system has been used to examine the effect of newly designed inhibitors of the MEP pathway and inhibitors of sterol biosynthesis such as squalestatin, terbinafine and Ro48-8071. In addition, we also studied the impact of different post-prenylation inhibitors or those suspected to affect the transport of proteins to the plasma membrane on the localization of the geranylgeranylable fusion protein GFP-BD-CVIL.

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Effects of in vivo and in vitro alkali treatment on intracellular pH regulation of OMCDis cells

AJP Renal Physiology ◽

10.1152/ajprenal.1993.265.5.f729 ◽

1993 ◽

Vol 265 (5) ◽

pp. F729-F735

Author(s):

M. Hayashi ◽

M. Iyori ◽

Y. Yamaji ◽

T. Saruta

Keyword(s):

Intracellular Ph ◽

Cell Function ◽

Ph Regulation ◽

Alkali Treatment ◽

Acid Base ◽

Acetoxymethyl Ester ◽

Functional Changes ◽

Significant Difference

To examine functional changes of the transporters in the inner stripe of the outer medullary collecting ducts (OMCDis) by the peritubular acid-base status, in vitro microperfusion using the acetoxymethyl ester of 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein was performed. Cell alkalinization systems were assessed by the recovery rate (dpHi/dt) of intracellular pH (pHi) after intracellular acid loading by NH(4+)-NH3 prepulse with bath amiloride. In alkali-loaded rabbits (0.15 M NaHCO3 drinking for 14 days), dpHi/dt showed a significant decrease (1.80 +/- 0.29 pH units/s x 10(3)) compared with either control (3.30 +/- 0.59) or acid-loaded rabbits (0.15 M NH4Cl drinking for 14 days, 3.05 +/- 0.46). The difference of dpHi/dt between control and alkali-loaded rabbits was eliminated by lumen N-ethylmaleimide (NEM), suggesting that H+ pump activity was decreased. The effect of in vitro alkali treatment (50 mM HCO3-, pH 7.7) for 3-4 h was also examined. This incubation significantly decreased the dpHi/dt (1.83 +/- 0.35) compared with the time control experiments (3.18 +/- 0.28), whereas no significant difference was seen in the presence of lumen NEM. Anion exchanger activity, as determined from the pHi changes after Cl- addition to the bath, showed no significant change with in vivo or in vitro alkali treatment. The results indicate that cell function of the OMCDis is regulated in response to the peritubular acid-base environment via changes in the H(+)-adenosinetriphosphatase.

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Effects of four extenders on the quality of frozen semen in Arabian stallions

Veterinary World ◽

10.14202/vetworld.2019.34-40 ◽

2019 ◽

Vol 12 (1) ◽

pp. 34-40 ◽

Cited By ~ 3

Author(s):

Mohaammed Saad Alamaary ◽

Haron Wahid ◽

Mohamed Ali ◽

Mark Wen Han Hiew ◽

Lawan Adamu ◽

...

Keyword(s):

Plasma Membrane ◽

Membrane Integrity ◽

Plasma Membrane Integrity ◽

Frozen Semen ◽

Before And After ◽

Semen Preservation ◽

The Impact

Aim: Different types of extenders have a variety of components which show the tolerance effect on sperm protection during freezing procedures. In the present study, we have examined the impact of the extenders HF-20 and Tris, which were locally manufactured, and they are competing with commercial extenders INRA Freeze® (IMV Technologies, France) and EquiPlus Freeze® (Minitube, Germany) on the quality of horses frozen semen. Materials and Methods: A total of 15 ejaculates from three healthy stallions were collected and cryopreserved in the same environment. Each semen sample collected was divided into four equal parts and processed. All samples were analyzed before and after freezing for motility, viability, plasma membrane integrity, and morphology. Furthermore, twenty mares were inseminated using post-thawed semen. Results: There were no differences observed among all extenders in all the parameters before freezing. Sperm cryopreserved using HF-20 showed better motility, viability, and plasma membrane integrity than Tris extender. The Tris extender showed the most inferior quality of post-thawed semen between all the extenders. HF-20, INRA Freeze®, and EquiPlus Freeze® extenders revealed the same capacity of semen preservation in vitro and in vivo. Conclusion: HF-20 extender has the same quality as INRA Freeze® and EquiPlus Freeze® that can be considered as one of the best extenders for the semen cryopreservation in horses. In contrast, Tris extender needs some degree of improvement.

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A Diagram to Facilitate the Understanding and Therapy of Mixed Acid Base Disorders

Anaesthesia and Intensive Care ◽

10.1177/0310057x7600400313 ◽

1976 ◽

Vol 4 (3) ◽

pp. 245-253 ◽

Cited By ~ 5

Author(s):

L. I. G. Worthley

Keyword(s):

Ph Regulation ◽

Case Reports ◽

Extracellular Fluid ◽

Carbon Dioxide Tension ◽

Acid Base ◽

Compensatory Response ◽

Mixed Acid ◽

Base Disorder ◽

Physiological Approach

A diagram based on in-vivo relationships between arterial hydrogen ion activity (H+) and carbon dioxide tension (PCO2 ) in primary abnormalities of acid base homeostasis is presented. It is designed to facilitate the interpretation of pH data by including the 95% confidence limits described in patients with simple metabolic and respiratory acid base disorders. These bands have been formulated from observation of simple acid base abnormalities and indicate the appropriate respiratory or renal compensatory response to the primary pH defect. A plot which falls outside these limits therefore indicates the presence of a mixed acid base disorder. The diagram presents a physiological approach to clinical disorders of pH regulation demonstrating maintenance of intra-cellular fluid homeostasis during primary extracellular fluid disturbances. Diagnostic and therapeutic advantages are further illustrated and discussed in six case reports.

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Proton export alkalinizes intracellular pH and reprograms carbon metabolism to drive hematopoietic progenitor growth

Blood ◽

10.1182/blood.2021011563 ◽

2021 ◽

Author(s):

Cheuk Him Man ◽

Francois Emile Mercier ◽

Nian Liu ◽

Wentao Dong ◽

Gregory Stephanopoulos ◽

...

Keyword(s):

Cell Growth ◽

Intracellular Ph ◽

Carbon Metabolism ◽

Carbon Flux ◽

Myeloid Leukemia ◽

Pentose Phosphate ◽

Competitive Growth ◽

Animal Cells ◽

The Warburg Effect

Proton export is often considered a detoxifying process in animal cells with monocarboxylate symporters co-exporting excessive lactate and protons during glycolysis or the Warburg effect. Here we report a novel mechanism by which lactate/H+ export is sufficient to induce cell growth. Increased lactate/proton export induces intracellular alkalization that selectively activates catalysis by key metabolic gatekeeper enzymes, HK1/PKM2/G6PDH, thereby enhancing glycolytic and pentose phosphate pathway carbon flux. The result is increased nucleotide levels, NADPH/NADP+ ratio and cell proliferation. Simply increasing the lactate/proton symporter, MCT4, or sodium-proton antiporter, NHE1 was sufficient to increase intracellular-pH (pHi) and give normal hematopoietic cells a significant competitive growth advantage in vivo. This process does not require additional cytokine triggers and is exploited in malignancy where leukemogenic mutations epigenetically increase MCT4. Inhibiting MCT4 decreased intracellular pH, carbon flux and eliminated acute myeloid leukemia-initiating-cells without cytotoxic chemotherapy. Intracellular alkalization is a primitive mechanism by which proton partitioning can directly reprogram carbon metabolism for cell growth.

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Annexins sense changes in intracellular pH during hypoxia

Biochemical Journal ◽

10.1042/bj20071116 ◽

2007 ◽

Vol 409 (1) ◽

pp. 65-75 ◽

Cited By ~ 35

Author(s):

Katia Monastyrskaya ◽

Fabian Tschumi ◽

Eduard B. Babiychuk ◽

Deborah Stroka ◽

Annette Draeger

Keyword(s):

Plasma Membrane ◽

Intracellular Ph ◽

Fluorescent Proteins ◽

Annexin A2 ◽

Transport Systems ◽

Physiological Parameter ◽

Membrane Association ◽

Ph Dependent

The pHi (intracellular pH) is an important physiological parameter which is altered during hypoxia and ischaemia, pathological conditions accompanied by a dramatic decrease in pHi. Sensors of pHi include ion transport systems which control intracellular Ca2+ gradients and link changes in pHi to functions as diverse as proliferation and apoptosis. The annexins are a protein family characterized by Ca2+-dependent interactions with cellular membranes. Additionally, in vitro evidence points to the existence of pH-dependent, Ca2+-independent membrane association of several annexins. We show that hypoxia promotes the interaction of the recombinant annexin A2–S100A10 (p11) and annexin A6 with the plasma membrane. We have investigated in vivo the influence of the pHi on the membrane association of human annexins A1, A2, A4, A5 and A6 tagged with fluorescent proteins, and characterized this interaction for endogenous annexins present in smooth muscle and HEK (human embryonic kidney)-293 cells biochemically and by immunofluorescence microscopy. Our results show that annexin A6 and the heterotetramer A2–S100A10 (but not annexins A1, A4 and A5) interact independently of Ca2+ with the plasma membrane at pH 6.2 and 6.6. The dimerization of annexin A2 within the annexin A2–S100A10 complex is essential for the pH-dependent membrane interaction at this pH range. The pH-induced membrane binding of annexins A6 and A2–S100A10 might have consequences for their functions as membrane organizers and channel modulators.

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