scholarly journals Extra- and Intracellular pH in the Brain during Seizures and in the Recovery Period following the Arrest of Seizure Activity

1985 ◽  
Vol 5 (1) ◽  
pp. 47-57 ◽  
Author(s):  
Bo K. Siesjö ◽  
Roger von Hanwehr ◽  
Görel Nergelius ◽  
Gunilla Nevander ◽  
Martin Ingvar
Keyword(s):  
Lactic Acid ◽  
Intracellular Ph ◽  
Seizure Activity ◽  
Lactic Acid Production ◽  
Recovery Period ◽  
Extracellular Fluid ◽  
The Difference ◽  
Lactate Levels ◽  
The Brain ◽  
Ph Microelectrodes

The objective of the study was to estimate changes in extracellular pH (pHe) and intracellular pH (pHi) during seizures and in the recovery period following the arrest of seizure activity. Seizures of 5- and 20-min duration were induced in rats by fluorothyl added to the insufflated gas mixture, and recovery for 5, 15, and 45 min was instituted by withdrawal of the fluorothyl supply following 20 min of continuous seizures. Changes in pHe were measured by double-barreled, liquid ion-exchange pH microelectrodes, and in pHi by the CO2 method, following estimation of tissue PCO2 and extracellular fluid (ECF) volume. The animals were either normoxic or rendered moderately hypoxic (arterial Po2 40–50 mm Hg). Upon induction of seizures in normoxic animals, pHe decreased by a mean of 0.36 unit, the values being identical at 5 and 20 min. In moderate hypoxia, seizures sustained for 20 min were accompanied by a further fall in pHe (mean decrease 0.51 unit). The changes in pHe seemed mainly to reflect the nonionic diffusion of lactic acid from cells to the ECF (tissue lactate levels ∼ 10 and 15 μmol g−1 during seizures in normoxic and hypoxic animals, respectively). However, the gradual fall in pHe attributable to lactic acid production was preceded by rapid acidification, sometimes exceeding the steady-state values subsequently attained. This acidification was interpreted to reflect spreading depression and fast transcellular Na+/H+ exchange. Following cessation of seizure discharge, pHe normalized at a surprisingly slow rate, with some acidosis persisting even after 45 min. The difference between cerebrovenous and arterial Pco2 was reduced during seizures and increased in the recovery period, probably reflecting alterations in the blood flow/metabolic rate coupling. Impedance changes were slight, indicating only minor changes in ECF volume. Changes in pHi after 5 min of seizures ranged from 0.20 (normoxic animals) to 0.32 (hypoxic animals) unit, the pHi values after 20 min being 0.07–0.08 unit higher. The results suggest the regulation of pHi during ongoing seizures. Upon arrest of seizure activity, pHi rapidly increased to normal and subsequently to supranormal values. Postepileptic intracellular alkalosis occurred at a time when pHe was still reduced and in spite of the fact that tissue lactate values had not normalized. It is concluded that the rapid normalization of pHi and overt alkalosis were caused by the simultaneously occurring oxidation of lactate, with the removal of a stoichiometrical amount of H+, and the extrusion of H+ from cells, possibly via a Na+/H+ exchanger, the latter probably delaying normalization of pHe.

scholarly journals Intracellular pH in the Brain following Transient Ischemia

1983 ◽  
Vol 3 (1) ◽  
pp. 109-114 ◽  
Author(s):  
Hideo Mabe ◽  
Photjanee Blomqvist ◽  
Bo K. Siesjö
Keyword(s):  
Creatine Kinase ◽  
Lactic Acid ◽  
Intracellular Ph ◽  
Adenine Nucleotides ◽  
Recovery Period ◽  
Transient Ischemia ◽  
Vessel Occlusion ◽  
Atp Production ◽  
Creatine Kinase Reaction ◽  
The Brain

The objective of the present study was to discover whether or not intracellular alkalosis develops in the brain in the recovery period following transient ischemia. Forebrain ischemia of 15-min duration was induced by four-vessel occlusion in rats, with recovery periods of 15, 60, and 180 min. Intracellular pH was derived both by the HCO3−–H2CO3 method and from the creatine kinase equilibrium. The ischemia was associated with energy failure and marked accumulation of lactic acid in the cerebral cortex. Recirculation brought about rapid rephosphorylation of adenine nucleotides and gradual normalization of lactic acid levels. After 15 min of recovery, the HCO3−–H2CO3 method indicated persisting acidosis, but the creatine kinase reaction did not. After 60 min, a shift of pH in the alkaline direction was demonstrated in both methods. This alkalosis had disappeared after 3 h of recovery. It is concluded that resumption of ATP production after ischemia is followed by a rapid rise in intracellular pH, which transiently increases above normal.

scholarly journals Improvement of Lactic Acid Production in Saccharomyces cerevisiae by Cell Sorting for High Intracellular pH

2006 ◽  
Vol 72 (8) ◽  
pp. 5492-5499 ◽  
Author(s):  
Minoska Valli ◽  
Michael Sauer ◽  
Paola Branduardi ◽  
Nicole Borth ◽  
Danilo Porro ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactic Acid ◽  
Intracellular Ph ◽  
Cell Sorting ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Low Ph ◽  
The Mean ◽  
High Level ◽  
Lactate Dehydrogenases

ABSTRACT Yeast strains expressing heterologous l-lactate dehydrogenases can produce lactic acid. Although these microorganisms are tolerant of acidic environments, it is known that at low pH, lactic acid exerts a high level of stress on the cells. In the present study we analyzed intracellular pH (pHi) and viability by staining with cSNARF-4F and ethidium bromide, respectively, of two lactic-acid-producing strains of Saccharomyces cerevisiae, CEN.PK m850 and CEN.PK RWB876. The results showed that the strain producing more lactic acid, CEN.PK m850, has a higher pHi. During batch culture, we observed in both strains a reduction of the mean pHi and the appearance of a subpopulation of cells with low pHi. Simultaneous analysis of pHi and viability proved that the cells with low pHi were dead. Based on the observation that the better lactic-acid-producing strain had a higher pHi and that the cells with low pHi were dead, we hypothesized that we might find better lactic acid producers by screening for cells within the highest pHi range. The screening was performed on UV-mutagenized populations through three consecutive rounds of cell sorting in which only the viable cells within the highest pHi range were selected. The results showed that lactic acid production was significantly improved in the majority of the mutants obtained compared to the parental strains. The best lactic-acid-producing strain was identified within the screening of CEN.PK m850 mutants.

Bicarbonate ion modulation of cerebral blood flow during hypoxia and hypercapnia

1982 ◽  
Vol 243 (1) ◽  
pp. H33-H40 ◽  
Author(s):  
R. C. Koehler ◽  
R. J. Traystman
Keyword(s):  
Blood Flow ◽  
Cerebrospinal Fluid ◽  
Cerebral Blood Flow ◽  
Lactic Acid ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Extracellular Fluid ◽  
Contralateral Side ◽  
Relative Importance ◽  
Anesthetized Dogs

The relative importance of changes in extracellular fluid (ECF) pH in mediating increases in cerebral blood flow (CBF) during hypoxia and hypercapnia was assessed by varying [HCO(-3)]ECF in pentobarbital-anesthetized dogs. Blood flow to one caudate nucleus (CNBF) that was bathed by cerebrospinal fluid (CSF) of varied [HCO(-3)] was compared with CNBF (measured by radiolabeled microspheres) on the contralateral side, which received a normal-[HCO(-3)]CSF perfusate. Raising [HCO(-3)]CSF from 25 to 60 meq/l for 150 min lowered CNBF by 16% and suppressed the slope of cNBF response to hypercapnia by 61% but suppressed the slope of CNBF response to hypoxia significantly less (22%). Lowering [HCO(-3)]CSF to 8 meq/l increased CNBF by 71% and augmented the response to hypercapnia by 126% but did not alter the slope of the response to hypoxia. These data indicate that changes in [H+]ECF can account for the increased CBF during hypercapnia but not for the entire hypoxic response. The increase in lactic acid production that would be necessary to solely account for the increase in CBF during hypoxia is much greater than what has been reported in the literature.

scholarly journals Regulation and Modulation of pH in the Brain

2003 ◽  
Vol 83 (4) ◽  
pp. 1183-1221 ◽  
Author(s):  
MITCHELL CHESLER
Keyword(s):  
Intracellular Ph ◽  
Neural Activity ◽  
Extracellular Fluid ◽  
Cell Types ◽  
Brain Regions ◽  
Metabolic Products ◽  
Homeostatic Function ◽  
Acid Extrusion ◽  
Activity Dependent ◽  
The Brain

Chesler, Mitchell. Regulation and Modulation of pH in the Brain. Physiol Rev 83: 1183-1221, 2003; 10.1152/physrev.00010.2003.—The regulation of pH is a vital homeostatic function shared by all tissues. Mechanisms that govern H+ in the intracellular and extracellular fluid are especially important in the brain, because electrical activity can elicit rapid pH changes in both compartments. These acid-base transients may in turn influence neural activity by affecting a variety of ion channels. The mechanisms responsible for the regulation of intracellular pH in brain are similar to those of other tissues and are comprised principally of forms of Na+/H+ exchange, Na+-driven Cl-/HCO3- exchange, Na+-HCO3- cotransport, and passive Cl-/HCO3- exchange. Differences in the expression or efficacy of these mechanisms have been noted among the functionally and morphologically diverse neurons and glial cells that have been studied. Molecular identification of transporter isoforms has revealed heterogeneity among brain regions and cell types. Neural activity gives rise to an assortment of extracellular and intracellular pH shifts that originate from a variety of mechanisms. Intracellular pH shifts in neurons and glia have been linked to Ca2+ transport, activation of acid extrusion systems, and the accumulation of metabolic products. Extracellular pH shifts can occur within milliseconds of neural activity, arise from an assortment of mechanisms, and are governed by the activity of extracellular carbonic anhydrase. The functional significance of these compartmental, activity-dependent pH shifts is discussed.

Amelioration of hypoxia-induced lactic acidosis by superimposed hypercapnea or hydrochloric acid infusion

1986 ◽  
Vol 250 (4) ◽  
pp. F702-F709 ◽  
Author(s):  
S. Abu Romeh ◽  
R. L. Tannen
Keyword(s):  
Lactic Acid ◽  
Metabolic Acidosis ◽  
Lactic Acidosis ◽  
Blood Lactate ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Respiratory Acidosis ◽  
Control Mechanisms ◽  
Lactate Levels ◽  
Blood Lactate Levels

Recent studies have shown that ketoacid production is exquisitely sensitive to changes in systemic pH, with a decrease inhibiting and an increase stimulating the production rate. To determine whether inhibition of net endogenous acid production is a widely applicable mechanism for the defense of acid-base homeostasis, we examined the effect of superimposed acidosis on lactic acid production by hypoxic rats. Anesthetized paralyzed mechanically ventilated rats with normocapnia increased blood lactate progressively in response to a fractional inspired O2 (FIO2) of 8% (PaO2, 35-38 mmHg) and achieved a level of 7.0 +/- 1.2 mM at 3 h. Superimposition of either mild respiratory acidosis (PCO2, 59 mmHg) or exogenous inorganic metabolic acidosis (intra-arterial HCl sufficient to decrease pH from 7.33 to 7.23) after 1 h of hypoxia dramatically diminished the rise in blood lactate. At the end of the third hour, blood lactate levels averaged 1.7 +/- 0.6 mM with superimposed respiratory acidosis and 2.7 +/- 0.4 mM with superimposed metabolic acidosis, both values being significantly less than the hypoxic controls. Termination of the superimposed respiratory acidosis resulted in a rapid increase in blood lactate levels, demonstrating the reversibility of the pH modulation of lactic acid production. Thus systemic acidosis appears to feed back in a protective fashion to inhibit net lactic acid production in rats with hypoxia-induced lactic acidosis. These findings suggest that finely tuned feedback control mechanisms that keep systemic pH within a narrow range operate under both major conditions of enhanced endogenous acid production (i.e., keto- and lactic acidosis).

Ventral medullary extracellular fluid pH and blood flow during hypoxia

1982 ◽  
Vol 242 (3) ◽  
pp. R195-R198 ◽  
Author(s):  
W. F. Nolan ◽  
P. C. Houck ◽  
J. L. Thomas ◽  
D. G. Davies
Keyword(s):  
Blood Flow ◽  
Extracellular Fluid ◽  
Brain Blood Flow ◽  
Vascular Response ◽  
Radioactive Microspheres ◽  
Vascular Responses ◽  
Control Value ◽  
Total Brain ◽  
The Brain ◽  
Ph Microelectrodes

Vascular responses of the ventral medulla and total brain to 30-60 min of isocapnic hypoxia (PaO2 = 32 +/- 2 Torr) were examined using radioactive microspheres in anesthetized, paralyzed, and artificially ventilated cats. Ventral medullary extracellular fluid (ECF) pH was measured using pH microelectrodes with tip diameters of 1-2 micrometers. Total brain blood flow (Q) increased significantly from a control value of 53 +/- 8 (mean +/- SE) to 160 +/- 42 ml.100 g-1.min-1 following 30-60 min of hypoxia. Ventral medullary Q increased from 28 +/- 5 to 97 +/- 20 ml.100 g-1.min-1 and ECF pH decreased by 0.15 +/- 0.06 pH U. Q responses are attributable to decreased vascular resistance as arterial pressure remained constant. The sensitivity of the ventral medullary vasculature to isocapnic hypoxia did not differ from that of the brain as a whole. The results show that under the conditions of our experiment, the ventral medullary vascular response to hypoxia is not sufficient to stabilize local ECF pH. The observation of simultaneously reduced pH and increased Q is consistent with a role for ECF H+ in mediating the cerebrovascular response to hypoxia.

scholarly journals Striking Differences in Glucose and Lactate Levels between Brain Extracellular Fluid and Plasma in Conscious Human Subjects: Effects of Hyperglycemia and Hypoglycemia

2002 ◽  
Vol 22 (3) ◽  
pp. 271-279 ◽  
Author(s):  
Walid M. Abi-Saab ◽  
David G. Maggs ◽  
Tim Jones ◽  
Ralph Jacob ◽  
Vinod Srihari ◽  
...  
Keyword(s):  
Human Subjects ◽  
Intractable Epilepsy ◽  
Extracellular Fluid ◽  
Intracerebral Microdialysis ◽  
Brain Extracellular Fluid ◽  
Lactate Levels ◽  
A Site ◽  
Clamp Study ◽  
The Relationship ◽  
The Brain

Brain levels of glucose and lactate in the extracellular fluid (ECF), which reflects the environment to which neurons are exposed, have never been studied in humans under conditions of varying glycemia. The authors used intracerebral microdialysis in conscious human subjects undergoing electro-physiologic evaluation for medically intractable epilepsy and measured ECF levels of glucose and lactate under basal conditions and during a hyperglycemia–hypoglycemia clamp study. Only measurements from nonepileptogenic areas were included. Under basal conditions, the authors found the metabolic milieu in the brain to be strikingly different from that in the circulation. In contrast to plasma, lactate levels in brain ECF were threefold higher than glucose. Results from complementary studies in rats were consistent with the human data. During the hyperglycemia–hypoglycemia clamp study the relationship between plasma and brain ECF levels of glucose remained similar, but changes in brain ECF glucose lagged approximately 30 minutes behind changes in plasma. The data demonstrate that the brain is exposed to substantially lower levels of glucose and higher levels of lactate than those in plasma; moreover, the brain appears to be a site of significant anaerobic glycolysis, raising the possibility that glucose-derived lactate is an important fuel for the brain.

scholarly journals Changes in Extra- and Intracellular pH in the Brain during and following Ischemia in Hyperglycemic and in Moderately Hypoglycemic Rats

1986 ◽  
Vol 6 (5) ◽  
pp. 574-583 ◽  
Author(s):  
M. -L. Smith ◽  
R. von Hanwehr ◽  
B. K. Siesjö
Keyword(s):  
Lactic Acid ◽  
Intracellular Ph ◽  
Extracellular Ph ◽  
Forebrain Ischemia ◽  
Extracellular Acidosis ◽  
The Brain ◽  
Tissue Metabolites

Incomplete forebrain ischemia of 15-min duration was induced in rats made hyperglycemic or moderately hypoglycemic prior to ischemia. Tissue CO2 tension, CO2 content, labile tissue metabolites, and extracellular pH (pHe) were measured, and intracellular pH (pHi) was derived by calculation on the assumption that cerebral intracellular fluids can be lumped into one space. In hypoglycemic animals, mean tissue lactate content increased from 2 to 10 μmol g−1. Tissue CO2 content was virtually unchanged and the CO2 tension increased from ∼50 to ∼145 mm Hg. In hyperglycemic animals, tissue lactate content rose to 20 μmol g−1, and the CO2 content decreased by 25%, demonstrating that some CO2 was lost to the blood supplied by the remaining perfusion. Accordingly, tissue CO2 tension did not rise above 200 mm Hg. pHe was reduced in proportion to the amount of lactate accumulated, the values obtained in hypo- and hyperglycemic animals showing relatively little scatter (6.76 ± 0.03 and 6.25 ± 0.04, respectively). In hypoglycemic animals the extracellular HCO−3 concentration was virtually unchanged, demonstrating that any influx of lactic acid from the cells must have been accompanied by H+ efflux and/or HCO−3 influx via independent routes. In hyperglycemic animals [HCO−3]e fell by >10 μmol ml−1. In both groups [HCO−3]e was reduced during the first 5 min of recovery. Recovery of pHe was slower in hyper- than in hypoglycemic animals. During ischemia calculated pHi fell to 6.37 ± 0.04 and 5.95 ± 0.06 in hypo- and hyperglycemic animals, respectively. Differences in pHi were maintained for the first 15 min of recovery, but in both hypo- and hyperglycemic animals pHi had normalized after 30 min. It is concluded that preischemic hyperglycemia leads to a more pronounced intra- and extracellular acidosis than normo- and hypoglycemia, an acidosis that also resolves more slowly during recirculation.

Inhibitory effect of tumor cell–derived lactic acid on human T cells

Blood ◽  
2007 ◽  
Vol 109 (9) ◽  
pp. 3812-3819 ◽  
Author(s):  
Karin Fischer ◽  
Petra Hoffmann ◽  
Simon Voelkl ◽  
Norbert Meidenbauer ◽  
Julia Ammer ◽  
...  
Keyword(s):  
T Cells ◽  
Lactic Acid ◽  
Cytokine Production ◽  
Lactic Acid Production ◽  
Recovery Period ◽  
Monocarboxylate Transporter ◽  
Immune Functions ◽  
Tumor Spheroids ◽  
Activated T Cells ◽  
Monocarboxylate Transporter 1

Abstract A characteristic feature of tumors is high production of lactic acid due to enhanced glycolysis. Here, we show a positive correlation between lactate serum levels and tumor burden in cancer patients and examine the influence of lactic acid on immune functions in vitro. Lactic acid suppressed the proliferation and cytokine production of human cytotoxic T lymphocytes (CTLs) up to 95% and led to a 50% decrease in cytotoxic activity. A 24-hour recovery period in lactic acid–free medium restored CTL function. CTLs infiltrating lactic acid–producing multicellular tumor spheroids showed a reduced cytokine production. Pretreatment of tumor spheroids with an inhibitor of lactic acid production prevented this effect. Activated T cells themselves use glycolysis and rely on the efficient secretion of lactic acid, as its intracellular accumulation disturbs their metabolism. Export by monocarboxylate transporter-1 (MCT-1) depends on a gradient between cytoplasmic and extracellular lactic acid concentrations and consequently, blockade of MCT-1 resulted in impaired CTL function. We conclude that high lactic acid concentrations in the tumor environment block lactic acid export in T cells, thereby disturbing their metabolism and function. These findings suggest that targeting this metabolic pathway in tumors is a promising strategy to enhance tumor immunogenicity.

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