Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The development of (Na+ + K+) ATPase, carbonic anhydrase and HCO3--stimulated ATPase activity was studied in developing rat brain in vivo, and in primary astrocyte cultures from 1--3-day-old rat brain as a function of increasing cell growth. The primary cultures showed an increase in all the above enzyme activities during cell growth, with time courses which were qualitatively similar to their development in vivo. Cell cultures grown separately from the cerebellum plus brain stem regions showed greater carbonic anhydrase activity than cerebral cultures over the entire 4-week growth period, corresponding to development of this activity in these same regions in vivo, HCO3-stimulated ATPase activity was slightly greater in cerebellar cultures and (Na+ + K+) ATPase activity was greater in cerebral cultures up to the second week of growth, resembling development of the same enzyme activities in vivo. C6 glioma and neuroblastoma cells showed no and 10-fold lower carbonic anhydrase activities respectively, compared to the primary astrocyte cultures. Addition of 1 mM N6-2'-O-dibutyryladenosine-3',5'-monophosphate (DBcAMP) in the presence of serum caused marked formation of cellular processes and increased carbonic anhydrase and (Na+ + K+) ATPase activity. Maximum effects were found 2 h after addition of 1 mM DBcAMP and thereafter declined. In the absence of serum such effects persisted for at least 24 h. Electron microscope studies showed large numbers of microtubule (approximately 20 nm diameter) and filamentous structures (less than or equal to 10 nm diameter) in the cytoplasm, which showed changes in distribution in cells treated with DBcAMP. This study suggests that the increase in ATPase and carbonic anhydrase activities in rat brain with increasing age may be in part a reflection of proliferation and development of astroglia cells. Together with the morphological data, it also provides additional evidence that primary cultures derived from neonatal rats may closely resemble developing astroglia in vivo.
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PMID:Enzymatic and morphological properties of primary rat brain astrocyte cultures, and enzyme development in vivo. 20 76

Human glioma (U-118 MG, U-251 MG) and human colon carcinoma (HT-29) spheroids and monolayers were continuously exposed to amiloride under physiological Na+ and HCO3- conditions. Amiloride in concentrations of 0.1-0.2 mM inhibited growth, while 0.5 mM or higher induced disintegration of the glioma spheroids within 4-6 days. Growth retardation of the HT-29 spheroids was achieved at concentrations of 0.4-0.5 mM and total growth inhibition and disintegration were achieved at 1.0 mM. Monolayer cultures of glioma cells were also more sensitive to amiloride than those of colon carcinoma cells. The higher amiloride concentrations induced pyknotic nuclei mainly in the central areas of the spheroids where the extracellular pH (pHe) was low. The amiloride-sensitive glioma spheroids had lower pHe than the colon carcinoma spheroids. The intracellular pH (pHi), measured in monolayers, was higher (7.11-7.18) in glioma cells than in colon carcinoma cells (6.94). High concentrations of amiloride, 1.0 mM for 1 h in combination with low Na+ concentrations, caused a strong pHi decrease in glioma cells but only a slight decrease in the colon carcinoma cells. The pHi measurements in glioma monolayers were carried out after 2-6 days of continuous exposure to 0.1 mM amiloride at physiological levels of Na+ and HCO3- to simulate the conditions during growth inhibition. After several days this caused, when growth already was inhibited, an acidification of pHi. Parallel measurements with X-ray microanalysis showed an increase of intracellular sodium and a decrease of intracellular potassium in the gliomas, while no such changes were seen in the colon carcinoma cells under identical conditions. It is concluded that the two glioma cell lines were more sensitive to amiloride, both as monolayers and spheroids, than the corresponding cultures of the colon carcinoma cell line. The inhibition of proliferation by amiloride seemed not to have a clear connection to pHi regulation.
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PMID:Effects of amiloride treatment on U-118 MG and U-251 MG human glioma and HT-29 human colon carcinoma cells. 184 15

Effects of severe lactacidosis were analyzed in vitro by employment of C6 glioma cells and astrocytes from primary culture. The cells were suspended in a physiological medium, which was rendered acidotic by addition of lactic acid in rising concentrations. A pH range of 7.4-4.2 was studied under maintenance of isotonicity and a normal electrolyte concentration of the medium. Cell swelling was quantified by flow cytometry using an advanced Coulter system with hydrodynamic focusing. The method was also utilized for assessment of cell viability by exclusion of the fluorescent dye propidium iodide. The volume of C6 glioma cells was found to increase if the pH was titrated to pH 6.8 or below. From this level downward, the extent of cell swelling depended on the degree of acidosis and the duration of exposure. For example, lactacidosis of pH 6.2 for 60 min led to an increase in cell size to 124.5% of normal, while pH 5.0 or 4.2 led to a cell size of 151.1 or 190.9%, respectively. A comparative analysis of the acidosis-induced cell swelling was made by using sulfuric acid. Swelling of C6 glioma at a given pH was only half of what was found when using lactic acid. This indicates specific swelling-inducing properties of lactic acid, while cell viability was not differently affected by both acids. Of the C6 glioma cells, 89.1% were viable under control conditions at pH 7.4. The viability remained unchanged down to pH 6.2. At pH 5.6, viability remained normal for 30 min, but it decreased to 73.4% after 60 min. Further lowering of pH to 5.0 or 4.6 respectively, decreased the number of viable cells to 47.8 or 40.3%. At pH 4.2 only 21.1% of the cells were surviving 1 h of lactacidosis. Cell swelling from lactacidosis could be largely inhibited by replacement of Na+ and bicarbonate ions in the medium by choline chloride and N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer, suggesting an involvement of the Na+/H+ and Cl-/HCO3- antiporters in the swelling process. Omission of Na+ and bicarbonate was, however, associated with reduced viability of the glial cells in acidosis. The swelling response of astrocytes obtained from primary culture was similar to that of C6 glioma. Lactic acid was also more effective in inducing cell swelling than sulfuric acid at the same level of acidosis. In astrocytes, viability at, e.g., pH 5.6 appeared to be more affected by lactic than by sulfuric acid.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Effects of lactacidosis on glial cell volume and viability. 221 80

Intracellular and extracellular acidosis may determine the ultimate outcome for brain tissue in cerebral ischemia. An extracellular acidosis that occurs in the penumbra zone was investigated in vitro as to its role in the formation of cytotoxic cell swelling. For that purpose, C6 glioma cells or primary cultured astrocytes were suspended in normal isotonic medium in normoxia during acidification to a final pH of 6.2. The cell volume response was determined by flow cytometry using hydrodynamic focusing, which allows one to recognize changes in cell size of less than 1%. A threshold pH of 6.8 was found that had to be crossed to induce cell swelling by acidosis. Once pH fell below this threshold, the increase in cell size appeared to be an all-or-nothing phenomenon. The cells rapidly assumed a final cell size of 115% of normal in the case of C6 glioma or of 118% in the case of primary cultured astrocytes independent of the actual level of acidosis or the duration of exposure. Acidosis-induced glial swelling could be significantly attenuated by 1) addition of amiloride, 2) administration of acetazolamide, or 3) replacement of bicarbonate buffer against N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES). Replacement of extracellular Na+ by choline chloride led to complete prevention of the acidosis-induced cell swelling. Taken together, the findings strongly indicate a central involvement of Na+/H+ and Cl-/HCO3- exchange mechanisms in the development of cell swelling under these conditions. Activation of the Na+/H+ antiporter can be considered an attempt to maintain a normal intracellular pH at the expense of an abnormal cell volume.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Glial swelling during extracellular acidosis in vitro. 335 26

Transport of SO4(2-) was studied in the glioma cell line LRM55 to determine whether it is mediated by the Cl-/HCO3- exchanger or the K+/Cl- cotransporter previously described in these cells (Wolpaw, E.W. and Martin, D.L. (1984) Brain Res. 297, 317-327). 35SO4(2-) influx was saturable with SO4(2-). External SO4(2-) stimulated 35SO4(2-) efflux, indicating an exchange mechanism. External Cl- was a competitive inhibitor of 35SO4(2-) influx. Internal Cl- stimulated 35SO4(2-) influx and external Cl- stimulated 35SO4(2-) efflux, indicating that Cl- is an exchange substrate for the SO4(2-) carrier. Also, SO4(2-) flux was sensitive to SITS, DIDS and furosemide. However, saturating external SO4(2-) did not inhibit 36Cl- influx and did not inhibit 36Cl- efflux via the Cl-/HCO3- exchanger. Moreover, K+ did not stimulate 36Cl- efflux via the Cl-/HCO3- exchanger. Moreover, K+ did not stimulate 35SO4(2-) influx as it does Cl- influx. These findings indicate that SO4(2-) transport into these cells is mediated by an exchange carrier distinct from both the Cl-/HCO3- exchanger and the K+/Cl- cotransporter. While Cl- is an alternative substrate for the SO4(2-) porter, this carrier is responsible for only a minor fraction of total Cl- flux in these cells.
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PMID:Sulfate-chloride exchange transport in a glioma cell line. 394 27

Swelling of glial and nerve cells is characteristic of brain damage in cerebral ischemia or trauma. The therapeutical efficiency of inhibition of Cl(-)-transport by a novel antagonist, the diuretic torasemide, on cytotoxic swelling of glial cells from lactacidosis, or glutamate was analyzed. Lactacidosis and the interstitial accumulation of glutamate are hallmarks of the pathophysiological alterations in ischemic or traumatic brain tissue. C6 glioma cells harvested from culture and suspended in a physiological medium were either exposed to pH 6.2, or 5.0 by lactic acid, or exposed to 1 mM glutamate at normal pH. Cell swelling and viability were quantified by flow cytometry. Lactacidosis of pH 6.2 led to an increase in cell volume to 117.9 +/- 0.7% within 60 min. Torasemide (1 mM) inhibited the swelling response by 50% (P < 0.01). Cell swelling at pH 5.0, although more severe, was again attenuated by torasemide (P < 0.01). No effect was seen on the decrease in cell viability at this level of acidosis. Addition of glutamate led to a steady increase in cell volume which, contrary to cell swelling from lactacidosis, was not inhibited by torasemide. Inhibition of cell swelling from acidosis by this diuretic may be attributed to blocking of Cl-/HCO3- exchange mechanisms activated by acidosis. The lack of effect by torasemide in glial cell swelling from glutamate indicates operation of a different mechanism inducing cell swelling, for example cellular accumulation of the amino acid together with Na+ and water.
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PMID:Swelling of glial cells in lactacidosis and by glutamate: significance of Cl(-)-transport. 768 80

We used the pH-sensitive fluorescent dye BCECF to study intracellular pH (pHi) regulation in primary cultures of rat astrocytes and C6 glioma cells. Both cell types contain three pH-regulating transporters: 1) alkalinizing Na+/H+ exchange; 2) alkalinizing Na+ + HCO3-/Cl- exchange; and 3) acidifying Cl-/HCO3- exchange. Na+/H+ exchange was most evident in the absence of CO2; recovery from acidification was Na+ dependent and amiloride sensitive. Exposure to CO2 caused a cell alkalinization that was inhibited by DIDS, dependent on external Na+, and inhibited 75% in the absence of Cl- (thus mediated by Na+ + HCO3-/Cl- exchange). When pHi was increased above the normal steady-state pHi, a DIDS-inhibitable and Na(+)-independent acidifying recovery was evident, indicating the presence of Cl-/HCO3- exchange. Astrocytes, but not C6 cells, contain a fourth pH-regulating transporter, Na(+)-HCO3- cotransport; in the presence of CO2, depolarization caused an alkalinization of 0.12 +/- 0.01 (n = 8) and increased the rate of CO2-induced alkalinization from 0.23 +/- 0.02 to 0.42 +/- 0.03 pH unit/min. Since C6 cells lack the Na(+)-HCO3- cotransporter, they are an inferior model of pHi regulation in glia. Our results differ from previous observations in glia in that: 1) Na+/H+ exchange was entirely inhibited by amiloride; 2) Na+ + HCO3-/Cl- exchange was present and largely responsible for CO2-induced alkalinization; 3) Cl-/HCO3- exchange was only active at pHi values above steady state; and 4) depolarization-induced alkalinization of astrocytes was seen only in the presence of CO2.
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PMID:Intracellular pH regulation in primary rat astrocytes and C6 glioma cells. 785 88

Volume regulation of C6 glioma cells was studied with an automatic system for monitoring cell thickness, while increasing bath osmolality from 300 to 440 mosmol/kgH2O. At 37 degrees C, tissues incubated in solutions containing active substances (inositol, D-biotin, hydrocortisone, prostaglandin E1, insulin, transferrin, sodium selenite, and 3,5,3'-triiodothyronine) responded to hyperosmotic challenge with a typical regulatory volume increase (RVI). Lowering temperature or removing the active substances inhibited osmoregulation. Bumetanide, amiloride, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, or ouabain significantly reduced RVI. Ion substitutions of Na+, Cl-, NaCl, or HCO3- also importantly affected the process. Extracellular acidification rate (EAR) was studied by microphysiometry. Hyperosmotic shock induced an increase in EAR with a time course that matched volume recovery. This increase in EAR was prevented by amiloride. The data show that under hyperosmotic conditions C6 cells are able to regulate their volume. Ion substitutions and application of blockers demonstrate that Na+/H+ and Cl-/HCO3- exchangers and Na(+)-K(-)-2Cl- cotransporter are involved in RVI. The rise in EAR is due to the enhanced activity of Na+/H+ antiporter, which seems to be volume dependent but not osmotic dependent.
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PMID:Electrolyte transport mechanisms involved in regulatory volume increase in C6 glioma cells. 889 8

1. Following ischaemic reperfusion, large amounts of superoxide anion (.O2-), hydroxyl radical (.OH) and H2O2 are produced, resulting in brain oedema and changes in cerebral vascular permeability. We have found that H2O2 (100 microM) induces a significant intracellular acidosis in both cultured rat cerebellar astrocytes (0.37 +/- 0.04 pH units) and C6 glioma cells (0.33 +/- 0.07 pH units). 2. Two membrane-crossing ferrous iron chelators, phenanthroline and deferoxamine, almost completely inhibited H2O2-induced intracellular acidosis, while the non-membrane-crossing iron chelator apo-transferrin had no effect. Furthermore, the acidosis was completely inhibited by two potent membrane-crossing .OH scavengers, N-(2-mercaptopropionyl)-glycine (N-MPG) and dimethyl thiourea (DMTU). Since .OH can be produced during iron-catalysed H2O2 breakdown (Fenton reaction), we have shown that a large reduction in pH1 in glial cells can result from the production of intracellular .OH via H2O2 oxidation. 3. We have ruled out the possible involvement of: (i) an increase in intracellular Ca2+ levels; and (ii) inhibition of oxidative phosphorylation. 4. Our results suggest that .OH inhibits glycolysis, leading to ATP hydrolysis and intracellular acidosis. This conclusion is based on the following observations: (i) in glucose-free medium, or in the presence of iodoacetate or 2-deoxy-D-glucose, H2O2-induced acidosis is completely suppressed; (ii) H2O2 and iodoacetate both produce an increase in levels of intracellular free Mg2+, an indicator of ATP breakdown; and (iii) direct measurement of intracellular ATP levels and lactate production show 50 and 55% reductions in ATP content and lactate production, respectively, following treatment with 100 microM H2O2. 5. Inhibition of the pH1 regulators (i.e. the Na(+)-H+ exchange and possibly the Na(+)-HCO3(-)-dependent pH1 transporters) resulting from H2O2-induced intracellular ATP reduction may also be involved in the H2O2-evoked intracellular acidosis in glial cells.
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PMID:Mechanism of oxidative stress-induced intracellular acidosis in rat cerebellar astrocytes and C6 glioma cells. 923 4

Hyperthermia has been introduced as a new modality of treatment for glioma. In these experiments, the cytotoxicity of hyperthermia in C6 glioma cells was enhanced by increasing the intracellular acidity with amiloride and/or 4,4'-diisothiocyanatostilbene-2,2' disulfonic acid (DIDS). Intracellular pH (pHi) is regulated mainly by Na+/H+ and HCO3-/Cl- antiports through the cell membrane, and amiloride acts on the former, DIDS on the latter to lower pHi. The cellular thermosensitivity to clinically achievable brain hyperthermia at 42 degrees C was enhanced by 0.5 mM amiloride (Na+/H+ antiport inhibitor). T0 values (T0 = the heating period required to reduce experimental survival rate by 1/e) at 42 degrees C without and with amiloride was 192 and 81 min, respectively. The addition of DIDS (HCO3-/Cl- antiport inhibitor) further enhanced. T0 value was 25 min. Fluorophotometric measurement of pHi was employed using the pH sensitive dye, bis(carboxyethyl)carboxyfluorescein, which is trapped in viable cells. The average pHi in control C6 glioma cells in pH 7.2 media was 7.21. In the untreated cells heated at 42 degrees C for 1 hour, the pHi was 7.12. The pHi of the cells heated in the presence of amiloride was decreased to 6.83. The pHi was further lowered to 6.67 by the treatment with amiloride in combination with DIDS for 2 hours. Hyperthermia with amiloride and DIDS may be a more effective treatment for malignant gliomas.
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PMID:Sensitization to hyperthermia by intracellular acidification of C6 glioma cells. 982 Nov 5


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