Extracellular Fluid pH Research Articles

The influence of seawater calcium ions on coral calcification mechanisms: Constraints from boron and carbon isotopes and B/Ca ratios in Pocillopora damicornis

In order to better understand the response of coral calcification to changes in seawater chemistry, fragments of the coral Pocillopora damicornis were grown in seawater with varying [Ca2+]. Using a combined trace element (B/Ca) and stable isotope (δ11B, δ13C) approach, this paper explores the effect of seawater calcium concentrations ([Ca2+]SW) on coral calcification mechanisms and describes the manipulation of the extracellular calcifying fluid (ECF) pH (pHECF), saturation state (ΩECF) and dissolved inorganic carbon (DIC) speciation of the ECF. In these experiments, increases in [Ca2+]SW did not significantly influence calcification rates but caused the skeletal B/Ca ratio to significantly increase. To explain these results we propose a mechanism by which [CO32−]ECF is influenced by [Ca2+]SW. This mechanism suggests that the pHECF will be lowest in our highest [Ca2+] treatment and using this relationship we can place constraints on the pHECF. The difference in pHECF in our treatments is supported in part by a slight, but insignificant decrease in skeletal δ11B and δ13C values. We propose a novel dual-proxy approach to estimate pHECF, where calcification occurs at a pHECF > 9. This work emphasizes the importance of multi-element proxy approaches in understanding pH up-regulation and CO32− concentrations during calcification of corals.

Timeless promotes the proliferation of hepatocellular carcinoma cell by reprogramming of glucose metabolism

Objective: To explore the function and molecular mechanism of Timeless in promoting hepatocellular carcinoma (HCC) growth. Methods: The expression of Timeless in HCC and paracancer tissues were analyzed by using the public data of HCC. Timeless was overexpressed in MHCC97L cells and silenced in MHCC97H cells, respectively, and the expression of Timeless and its downstream molecules were detected by real-time PCR and western blot. The effects of Timeless on cell glycolysis, oxidative phosphorylation and proliferation were detected by the glucose uptake experiment, lactic acid detection experiment, the extracellular fluid pH detection experiment, cell oxygen consumption test and cell viability assay, respectively. Results: The level of Timeless in HCC tissue was significantly higher than that of paracancer tissue (P<0.05). The relative cellular glucose uptake levels in the groups of Timeless knockdown, including siTimeless-1 and siTimeless-2 group were 0.510±0.119 and 0.508±0.099, respectively, significantly different from that of control group (P<0.05); The relative cellular uptake level of Timeless overexpressed group was 1.953±0.324, significantly different from that of vector transfected group (P<0.05). The relative levels of lactic acid production in the siTimeless-1 and siTimeless-2 group were 0.579±0.096 and 0.550±0.120, respectively, significantly different from that of control group (P<0.05); The relative production level of lactic acid in the Timeless overexpressed group was 1.463±0.179, significantly different that of vector transfected group (P<0.05). The extracellular pH values of siTimeless-1 and siTimeless-2 group were 7.390±0.035 and 7.370±0.060, respectively, significantly different from that of control group (P<0.05); the extracellular pH value of Timeless overexpressed group was 7.130±0.031, significantly different than vector transfected group (P<0.05). Oxygen consumption rate of siTimeless-1 and siTimeless-2 group were 3.686±0.389 and 3.955±0.431, respectively, significantly higher than 1.690±0.297 of control group (P<0.05); Oxygen consumption rate of Timeless overexpressed group was 1.302±0.336, significantly lower than 3.185±0.262 of vector transfected group (P<0.05) Timeless inhibited the expression of p53. The cell glucose uptake, lactic acid production, the pH of extracellular culture medium and cell oxygen consumption of control group were not significantly different from that of Timeless and p53 co-silenced group [(si-Timeless+sip53) group] (P>0.05); the glucose uptake, the production of lactic acid, the pH of the extracellular culture medium and the oxygen consumption of Timeless co-transfected with p53 (Timeless+p53) group were not significantly different from those of vector transfected group (P>0.05). Timeless promoted the proliferation of HCC cells through inhibiting the expression of p53. Conclusion: Timeless promotes reprogramming of glucose metabolism and proliferation of HCC cells by inhibiting the p53-dependent signaling pathway.

Extracellular Acid-Base Balance and Ion Transport Between Body Fluid Compartments.

Clinical assessment of acid-base disorders depends on measurements made in the blood, part of the extracellular compartment. Yet much of the metabolic importance of these disorders concerns intracellular events. Intracellular and interstitial compartment acid-base balance is complex and heterogeneous. This review considers the determinants of the extracellular fluid pH related to the ion transport processes at the interface of cells and the interstitial fluid, and between epithelial cells lining the transcellular contents of the gastrointestinal and urinary tracts that open to the external environment. The generation of acid-base disorders and the associated disruption of electrolyte balance are considered in the context of these membrane transporters. This review suggests a process of internal and external balance for pH regulation, similar to that of potassium. The role of secretory gastrointestinal epithelia and renal epithelia with respect to normal pH homeostasis and clinical disorders are considered. Electroneutrality of electrolytes in the ECF is discussed in the context of reciprocal changes in Cl- or non Cl- anions and [Formula: see text].

Ocean acidification increases copper toxicity differentially in two key marine invertebrates with distinct acid-base responses.

Ocean acidification (OA) is expected to indirectly impact biota living in contaminated coastal environments by altering the bioavailability and potentially toxicity of many pH-sensitive metals. Here, we show that OA (pH 7.71; pCO2 1480 μatm) significantly increases the toxicity responses to a global coastal contaminant (copper ~0.1 μM) in two keystone benthic species; mussels (Mytilus edulis) and purple sea urchins (Paracentrotus lividus). Mussels showed an extracellular acidosis in response to OA and copper individually which was enhanced during combined exposure. In contrast, urchins maintained extracellular fluid pH under OA by accumulating bicarbonate but exhibited a slight alkalosis in response to copper either alone or with OA. Importantly, copper-induced damage to DNA and lipids was significantly greater under OA compared to control conditions (pH 8.14; pCO2 470 μatm) for both species. However, this increase in DNA-damage was four times lower in urchins than mussels, suggesting that internal acid-base regulation in urchins may substantially moderate the magnitude of this OA-induced copper toxicity effect. Thus, changes in metal toxicity under OA may not purely be driven by metal speciation in seawater and may be far more diverse than either single-stressor or single-species studies indicate. This has important implications for future environmental management strategies.

Temporal fluctuations in seawater pCO2 may be as important as mean differences when determining physiological sensitivity in natural systems

AbstractMost studies assessing the impacts of ocean acidification (OA) on benthic marine invertebrates have used stable mean pH/pCO2 levels to highlight variation in the physiological sensitivities in a range of taxa. However, many marine environments experience natural fluctuations in carbonate chemistry, and to date little attempt has been made to understand the effect of naturally fluctuating seawater pCO2 (pCO2sw) on the physiological capacity of organisms to maintain acid–base homeostasis. Here, for the first time, we exposed two species of sea urchin with different acid–base tolerances, Paracentrotus lividus and Arbacia lixula, to naturally fluctuating pCO2sw conditions at shallow water CO2 seep systems (Vulcano, Italy) and assessed their acid–base responses. Both sea urchin species experienced fluctuations in extracellular coelomic fluid pH, pCO2, and [HCO3−] (pHe, pCO2e, and [HCO3−]e, respectively) in line with fluctuations in pCO2sw. The less tolerant species, P. lividus, had the greatest capacity for [HCO3−]e buffering in response to acute pCO2sw fluctuations, but it also experienced greater extracellular hypercapnia and acidification and was thus unable to fully compensate for acid–base disturbances. Conversely, the more tolerant A. lixula relied on non-bicarbonate protein buffering and greater respiratory control. In the light of these findings, we discuss the possible energetic consequences of increased reliance on bicarbonate buffering activity in P. lividus compared with A. lixula and how these differing physiological responses to acute fluctuations in pCO2sw may be as important as chronic responses to mean changes in pCO2sw when considering how CO2 emissions will affect survival and success of marine organisms within naturally assembled systems.

Analysis of Arterial and Venous Blood Gases in Healthy Gyr Falcons ( Falco rusticolus ) Under Anesthesia.

Arterial and venous blood gas analysis is useful in the assessment of tissue oxygenation and ventilation and in diagnosis of metabolic and respiratory derangements. It can be performed with a relatively small volume of blood in avian patients under emergency situations. Arterial and venous blood gas analysis was performed in 30 healthy gyr falcons ( Falco rusticolus ) under anaesthesia to establish temperature-corrected reference intervals for arterial blood gas values and to compare them to temperature-corrected venous blood gas values with a portable point-of-care blood gas analyzer (i-STAT 1, Abbott Laboratories, Abbott Park, IL, USA). Statistically significant differences were observed between the temperature-corrected values of pH, partial pressure of carbon dioxide (Pco2), and partial pressure of oxygen (Po2) and the corresponding nontemperature-corrected values of these parameters in both arterial and venous blood. Values of temperature-corrected pH, temperature-corrected Pco2, bicarbonate concentrations, and base excess of extra cellular fluid did not differ significantly between arterial and venous blood, suggesting that, in anesthetized gyr falcons, venous blood gas analysis can be used in place of arterial blood gas analysis in clinical situations. Values for hematocrit, measured by the point-of-care analyzer, were significantly lower compared with those obtained by the microhematocrit method.

Optimized conditions for primary culture of pituitary cells from the Atlantic cod (Gadus morhua). The importance of osmolality, pCO2, and pH

Protocols for primary cultures of teleost cells are commonly only moderately adjusted from similar protocols for mammalian cells, the main adjustment often being of temperature. Because aquatic habitats are in general colder than mammalian body temperatures and teleosts have gills in direct contact with water, pH and buffer capacity of blood and extracellular fluid are different in fish and mammals. Plasma osmolality is generally higher in marine teleosts than in mammals. Using Atlantic cod (Gadus morhua) as a model, we have optimized these physiological parameters to maintain primary pituitary cells in culture for an extended period without loosing key properties. L-15 medium with adjusted osmolality, adapted to low pCO2 (3.8mm Hg) and temperature (12°C), and with pH 7.85, maintained the cells in a physiologically sounder state than traditional culture medium, significantly improving cell viability compared to the initial protocol. In the optimized culture medium, resting membrane potential and response to releasing hormone were stable for at least two weeks, and the proportion of cells firing action potentials during spawning season was about seven times higher than in the original culture medium. The cells were moderately more viable when the modified medium was supplemented with newborn calf serum or artificial serum substitute. Compared to serum-free L-15 medium, expression of key genes (lhb, fshb, and gnrhr2a) was better maintained in medium containing SSR, whereas NCS tended to decrease the expression level. Although serum-free medium is adequate for many applications, serum supplement may be preferable for experiments dependent on membrane integrity.

Development of a pH sensitive nanocarrier using calcium phosphate coated gold nanoparticles as a platform for a potential theranostic material

Methoxy-poly(ethylene glycol) (mPEG)-Asp-Cys was synthesized by ring opening polymerization, and its characterization by 1H nuclear magnetic resonance (NMR) showed that the copolymer has 18 aspartic acid units and 0.95 cysteine units on average, with the molecular weight and distribution of 13.1 k and 1.15. PEGylated AuNP with doxorubicin containing CaP layers was prepared to have the size of 79.8±18.7 nm by light scattering measurement method, with the CaP thickness around 27 nm. PEGylated Dox-AuNP@CaP was stable in the physiological conditions for several weeks in the presence of glutathione. Loading amount and efficiency of doxorubicin into the particles were 1.3% and 27.9%, respectively. The loading amount was 1.3%, lower than common organic selfassembled carriers, because of the relatively high atomic mass of gold. In vitro release experiments were performed in two different environments: extracellular fluid (pH 7.4) and intracellular lyosomal fluid (pH 4.5). The amount of released doxorubicin from PEGylated Dox-AuNP, without CaP layer, exceeds 60% in 2 h. In contrast, PEGylated Dox-AuNP@CaP effectively limited the doxorubicin release in the extracellular condition to 13% after 12 h, and changing the media to the intracellular lysosomal condition resulted in a triggered release of doxorubicin from 7% to 78% in an additional 4 h. Cell viability of PEGylated Dox-AuNP@CaP and PEGylated AuNP@CaP were estimated with HeLa cells by MTT assay. Cell viability of PEGylated Dox-AuNP@CaP came down to 19% after 24 h incubation, while the PEGylated AuNP@CaP particle itself showed slight cytotoxicity with the same conditions. The prepared PEGylated Dox-AuNP@CaP worked as a pH- and ion concentration-sensitive drug-delivery system as well as theranostic nanoparticles for CT imaging and cancer treatment. Open image in new window

Assessing acid retention in humans

to the editor: Dr. Troels Ring ([8][1]) has asked important questions about our recent publication in the American Journal of Physiology-Renal Physiology ([12][2]) that interprets its data as supporting that humans with reduced estimated glomerular filtration rate (eGFR) have acid retention,

Plasma amino acid concentrations and mRNA expression of components related to protein degradation in lambs with nutritionally induced metabolic acidosis

Aspects of amino acid metabolism and proteolysis were examined in lambs with metabolic acidosis. Lambs (n = 30; 42.8 ± 4.1 kg BW) were randomly assigned to treatment groups, receiving a topdress of either (1) dried distiller’s grain (DDG; anion load of 7 mEq 100 g-1 DM, (2) DDG + NH4Cl-treated DDG (anionic load of -29 mEq 100 g-1 DM), or (3) DDG + NH4Cl-treated DDG (anionic load of -42 mEq 100 g-1 DM). Lambs were maintained on DDG topdress for 9 d, after which increasing amounts of DDG were substituted with NH4Cl-treated DDG in the treatment group diets from day 10 to day 21. Blood gas, blood acid-base, urine pH and plasma amino acid concentrations were determined on day 9 and day 21. On day 22, lambs were slaughtered and kidney, liver, extensor digitorum longus muscle (EDL), and soleus muscle samples were collected. Blood pH, bicarbonate, base excess of blood and extracellular fluid, total CO2 and urinary pH were linearly decreased as dietary anionic load increased (P &lt; 0.001). Plasma glutamine, glycine, histidine, arginine and asparagine increased linearly (P &lt; 0.06) due to acidosis, while renal glutamate dehydrogenase (P = 0.02) and hepatic glutamine synthetase (P = 0.02) mRNA expression were linearly increased. Caspase-3 mRNA expression was linearly decreased in soleus muscle by acidosis (P = 0.01), but not in EDL muscle. No change in mRNA expression of components of the ubiquitin-mediated proteolytic pathway was observed in either muscle. These results suggest muscle-specific regulation of caspase-3 mRNA expression during metabolic acidosis in sheep.

Commentaries on Viewpoint: Central chemoreception is a complex system function that involves multiple brain stem sites

to the editor: Amniote vertebrates adjust the acid-base status of the blood through ventilatory alterations of PaCO2 and, to some degree, by renal modulation of bicarbonate concentration. Receptor systems for the ventilatory acid-base regulation has been studied mainly in mammals, in which the

Na +/H + Exchangers in Renal Regulation of Acid-Base Balance

The kidney plays key roles in extracellular fluid pH homeostasis by reclaiming bicarbonate (HCO(3)(-)) filtered at the glomerulus and generating the consumed HCO(3)(-) by secreting protons (H(+)) into the urine (renal acidification). Sodium-proton exchangers (NHEs) are ubiquitous transmembrane proteins mediating the countertransport of Na(+) and H(+) across lipid bilayers. In mammals, NHEs participate in the regulation of cell pH, volume, and intracellular sodium concentration, as well as in transepithelial ion transport. Five of the 10 isoforms (NHE1-4 and NHE8) are expressed at the plasma membrane of renal epithelial cells. The best-studied isoform for acid-base homeostasis is NHE3, which mediates both HCO(3)(-) absorption and H(+) excretion in the renal tubule. This article reviews some important aspects of NHEs in the kidney, with special emphasis on the role of renal NHE3 in the maintenance of acid-base balance.

Effects on breathing in awake and sleeping goats of focal acidosis in the medullary raphe.

Our aim was to determine the effects of focal acidification in the raphe obscurus (RO) and raphe pallidus (RP) on ventilation and other physiological variables in both the awake and sleep states in adult goats. Through chronically implanted microtubules, 1) a focal acidosis was created by microdialysis of mock cerebrospinal fluid (mCSF), equilibrated with various levels of CO2, and 2) medullary extracellular fluid (ECF) pH was measured by using a custom-made pH electrode. Focal acidosis in the RO or RP, by dialyzing either 25 or 80% CO2 (mCSF pH approximately 6.8 or 6.3), increased (P < 0.05) inspiratory flow by 8 and 12%, respectively, while the animals were awake during the day, but not at night while they were awake or in non-rapid eye movement sleep. While the animals were awake during the day, there were also increases in heart rate and blood pressure (P < 0.05) but no significant change in metabolic rate or arterial Pco2. Dialysis with mCSF equilibrated with 25 or 80% CO2 reduced ECF pH by the same amount (25%) or three times more (80%) than when inspired CO2 was increased to 7%. During CO2 inhalation, the reduction in ECF pH was only 50% of the reduction in arterial pH. Finally, dialysis in vivo only decreased ECF pH by 19.1% of the change during dialysis in an in vitro system. We conclude that 1) the physiological responses to focal acidosis in the RO and RP are consistent with the existence of chemoreceptors in these nuclei, and 2) local pH buffering mechanisms act to minimize changes in brain pH during systemic induced acidosis and microdialysis focal acidosis and that these mechanisms could be as or more important to pH regulation than the small changes in inspiratory flow during a focal acidosis.

Hints of western medicine from Chinese medicine.

As a biochemist, I have been studying lipolytic and lipogenic pathways in fat cells since 1963. In 1966, I proposed a hormone-sensitive substrate theory in which catecholamines might not act on lipase but on substrate during their lipolytic processes. The lipolytic and lipogenic pathways are negative and positive processes in triglyceride content of fat cells. Insulin inhibits the negative process (lipolysis) and stimulates the positive process (lipogenesis from glucose). On the other hand, catecholamine stimulates the negative process and inhibits the positive one. These hormones discriminate the negative and positive rules and regulate opposite ways. We tried to find these hormone-like substances in various natural products. We isolated tea saponins, chitosan, and others as insulin-like substances and dimethyl-xanthine as a catecholamine-like one. It is well known that extracellular fluid pH changes from 7.4 to 6.8. Reduction of the pH from 7.4 causes insulin resistance. Insulin failed to stimulate glucose uptake at pH 7.0 of the extracellular fluid. We found minus ions, which stimulated lipogenesis from glucose by raising extracellular fluid pH to 7.4. These are our approaches to find functional substances that prevent lifestyle-related diseases.

An Intelligent MRI Contrast Agent for Tumor Sensing

An intelligent MRI contrast agent has been designed by taking advantage of a microenvironmental responsive polyion complex (PIC). The intelligent signal switching was achieved by controlling Gd ion-water interactions in the microenvironmental responsive PIC. MRI signal of the agent appeared only in tumor region, selectively, and did not appear in normal tissues, when the agent was administrated to a tumor-bearing mouse from the tail vein. The acidic microenvironment, such as lower extracellular fluid pH, higher expression of acidic proteins and polysaccharides, was suggested to cause the tumor-selective activation of the agent.

Acidosis and nutrition

In recent years there has been increasing evidence for the deleterious effect of acidosis on a number of fundamental systems of the body including nutrition [1, 2]. Approximately 70 mmol of hydrogen ions are produced daily by the body, and to maintain acid-base balance there must be an equivalent net acid secretion by the kidney. It is remarkable that extracellular fluid (ECF) pH is maintained within a very narrow range of 7.35-7.45 (35-45 nM), reflecting the fundamental importance of pH on many aspects of basic cellular function particularly proteins. It is important to differentiate between the terms acidosis and acidemia. The former is a pathophysiologic process tending to acidify body fluids, whereas the latter occurs when the ECF hydrogen ion concentration is above the normal range. It is possible to be acidotic (with a reduced serum bicarbonate) but not acidemic because of appropriate buffering of hydrogen ions. The major extracellular buffer is the carbonic acid/hydrogen carbonate system with plasma proteins and hemoglobin contributing significantly less. The major intracellular buffer is protein followed by bone [3]. The type of acidosis seen in patients with chronic renal failure changes with decreasing GFR; initially a non-anion gap acidosis is observed secondary to the loss of bicarbonate from the proximal tubule and impaired excretion in the distal tubule. With increasing severity of renal impairment, failure to excrete organic and inorganic acids results in an increased anion gap [4, 5].

This Month in the Journal

This Month in the Journal

Ventilatory effects of glial dysfunction in a rat brain stem chemoreceptor region.

Glia are thought to be important in brain extracellular fluid ion and pH regulation, but their role in brain stem sites that sense pH and stimulate breathing is unknown. Using a diffusion pipette, we administered the glial toxin, fluorocitrate (FC; 1 mM) into one such brain stem region, the retrotrapezoid nucleus (RTN) for 45-60 min. This dose and time period were chosen so that the effects of FC would be largely reversible. Within minutes, tissue pH decreased, and respiratory output increased. Both recovered almost completely after cessation of FC administration. The response to systemic CO2 stimulation was unaffected by FC treatment compared with that following control diffusion. Anatomic analysis showed, at the center of FC administration, some small (mean diameter = 5.1 micrometer) cells that stained for DEAD Red, a marker for altered cell membrane permeability, and some fragmented glia (glial fibrillary acidic protein immunohistochemistry). The average RTN tissue volume that contained such DEAD Red-positive cells was 271 nl, approximately 23% of the volume of one RTN region. Reversible disruption of glia in the RTN, a region known to contain central chemoreception, results in an acidic local pH and in stimulation of respiratory output.

This Month in the Journal

This Month in the Journal

Skeletal muscle ECF pH error signal for exercise ventilatory control.

An autonomic reflex linking exercising skeletal muscle metabolism to central ventilatory control is thought to be mediated by neural afferents having free endings that terminate in the interstitial fluid of muscle. To determine whether changes in muscle extracellular fluid pH (pHe) can provide an error signal for exercise ventilatory control, pHe was measured during electrically induced contraction by 31P-magnetic resonance spectroscopy and the chemical shift of a phosphorylated, pH-sensitive marker that distributes to the extracellular fluid (phenylphosphonic acid). Seven lightly anesthetized rats underwent unilateral continuous 5-Hz sciatic nerve stimulation in an 8.45-T nuclear magnetic resonance magnet, which resulted in a mixed lactic acidosis and respiratory alkalosis, with no net change in arterial pH. Skeletal muscle intracellular pH fell from 7.30 +/- 0.03 units at rest to 6.72 +/- 0.05 units at 2.4 min of stimulation and then rose to 7.05 +/- 0.01 units (P < 0.05), despite ongoing stimulation and muscle contraction. Despite arterial hypocapnia, pHe showed an immediate drop from its resting baseline of 7.40 +/- 0.01 to 7.16 +/- 0.04 units (P < 0.05) and remained acidic throughout the stimulation protocol. During the on- and off-transients for 5-Hz stimulation, changes in the pH gradient between intracellular and extracellular compartments suggested time-dependent recruitment of sarcolemmal ion-transport mechanisms. pHe of exercising skeletal muscle meets temporal and qualitative criteria necessary for a ventilatory metaboreflex mediator in a setting where arterial pH does not.