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Mancuso A, Beardsley NJ, Wehrli S, Pickup S, Matschinsky FM, Glickson JD. Real-time detection of 13C NMR labeling kinetics in perfused EMT6 mouse mammary tumor cells and betaHC9 mouse insulinomas. Biotechnol Bioeng 2005; 87:835-48. [PMID: 15334410 DOI: 10.1002/bit.20191] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A method was developed for obtaining high signal-to-noise 13C NMR spectra of intracellular compounds in metabolically active cultured cells. The method allows TCA cycle labeling kinetics to be determined in real time without significant oxygen transport limitations. Cells were immobilized on the surface of nonporous microcarriers that were either uncoated or coated with polypeptides and used in a 12-cm3 packed bed. The methods were tested with two EMT6 mouse mammary tumor cell lines, one strongly adherent and the other moderately adherent, and a weakly adherent mouse insulinoma line (betaHC9). For both EMT6 lines, NTP and oxygen consumption measurements indicated that the number of cells in the spectrometer ranged from 6 x 10(8) to 1 x 10(9). During infusion of [1-13C]glucose, labeling in C-4 glutamate (indicative of flux into the first half of the TCA cycle) could be detected with 15-min resolution. However, labeling for C-3 and C-2 glutamate (indicative of complete TCA cycle activity) was fivefold lower and difficult to quantify. To increase TCA cycle labeling, cells were infused with medium containing [1,6-13C2]glucose. A 2.5-fold increase was observed in C-4 glutamate labeling and C-3 and C-2 glutamate labeling could be monitored with 30-min resolution. Citrate synthase activity was indirectly detected in real time, as [3,4-13C2]glutamate was formed from [2-13C]oxaloacetate and [2-13C]acetate (of acetyl-CoA). Cell mass levels observed with betaHC9 cells were somewhat lower. However, the 13C S/N was sufficient to allow real-time monitoring of the response of intracellular metabolite labeling to a step change in glucose and a combined glutamine/serum pulse.
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Affiliation(s)
- A Mancuso
- Department of Radiology/6069, B6 Blockley Hall, 423 Guardian Drive, Philadelphia, Pennsylvania 19104-6021, USA.
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Pietri S, Martel S, Culcasi M, Delmas-Beauvieux MC, Canioni P, Gallis JL. Use of diethyl(2-methylpyrrolidin-2-yl)phosphonate as a highly sensitive extra- and intracellular 31P NMR pH indicator in isolated organs. Direct NMR evidence of acidic compartments in the ischemic and reperfused rat liver. J Biol Chem 2001; 276:1750-8. [PMID: 11013264 DOI: 10.1074/jbc.m008023200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The novel phosphorylated pyrrolidine diethyl(2-methylpyrrolidin-2-yl)phosphonate (DEPMPH) was evaluated as a (31)P NMR probe of the pH changes associated with ischemia/reperfusion of rat isolated hearts and livers. In vitro titration curves indicated that DEPMPH exhibited a 4-fold larger amplitude of chemical shift variation than inorganic phosphate yielding an enhanced NMR sensitivity in the pH range of 5.0-7.5 that allowed us to assess pH variations of less than 0.1 pH units. At the non-toxic concentration of 5 mm, DEPMPH distributed into external and cytosolic compartments in both normoxic organs, as assessed by the appearance of two resonance peaks. An additional peak was observed in normoxic and ischemic livers, assigned to DEPMPH in acidic vesicles (pH 5.3-5.6). During severe myocardial ischemia, a third peak corresponding to DEPMPH located in ventricular and atrial cavities appeared (pH 6.9). Mass spectrometry and NMR analyses of perchloric extracts showed that no significant metabolism of DEPMPH occurred in the ischemic liver. Reperfusion with plain buffer resulted in a rapid washout of DEPMPH from both organs. It was concluded that the highly pH-sensitive DEPMPH could be of great interest in noninvasive ex vivo studies of pH gradients that may be involved in many pathological processes.
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Affiliation(s)
- S Pietri
- Structure et Réactivité des Espèces Paramagnétiques, CNRS-UMR 6517 Universités d'Aix-Marseille I et III, F-13397 Marseille Cedex 20, France.
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3
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Pietri S, Miollan M, Martel S, Le Moigne F, Blaive B, Culcasi M. alpha - and beta -phosphorylated amines and pyrrolidines, a new class of low toxic highly sensitive 31P NMR pH indicators. Modeling of pKa and chemical shift values as a function of substituents. J Biol Chem 2000; 275:19505-12. [PMID: 10748044 DOI: 10.1074/jbc.m001784200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fourteen linear and cyclic alpha- and beta-aminophosphonates in which the P-atom is substituted by alkoxy groups have been synthesized and evaluated as (31)P NMR pH markers in Krebs-Henseleit buffer. pK(a) values varied with substitution in the range 1.3-9.1, giving potentially access to a wide range of pH. Temperature had a weak influence on pH and a dramatic increase in ionic strength slightly modified the pK(a) of the pyrrolidine diethyl(2-methylpyrrolidin-2-yl)phosphonate (DEPMPH). All compounds displayed a 4-fold better NMR sensitivity than inorganic phosphate or other commonly used phosphonates, as assessed by differences delta(b)-delta(a) between the chemical shifts of the protonated and the unprotonated forms. In isolated perfused rat hearts, a non-toxic concentration window of 1.5-15 mm was determined for three representative compounds. Using empirical linear relationships, the experimental values of pK(a), delta(a), and delta(b) have been correlated with the two-dimensional structure, i.e. the chemical nature of substituents bonded to the secondary amine and P-atom. The data suggest that DEPMPH and its cyclic and linear variants are ideal versatile (31)P NMR probes for the study of tenuous pH changes in biological processes.
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Affiliation(s)
- S Pietri
- Structure et Réactivité des Espèces Paramagnétiques, CNRS-UMR 6517, France.
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Szwergold BS, Kappler F, Moldes M, Shaller C, Brown TR. Characterization of a phosphonium analog of choline as a probe in 31P NMR studies of phospholipid metabolism. NMR IN BIOMEDICINE 1994; 7:121-127. [PMID: 8080713 DOI: 10.1002/nbm.1940070304] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Tumors and transformed cells have been shown by 31P NMR to contain elevated concentrations of two phosphomonoesters, phosphorylcholine and phosphorylethanolamine, involved in phospholipid metabolism. In order to understand the biochemical basis for these phenomena new methods are needed to allow for analysis of the relevant metabolic pathways in intact cells. One such promising tool may be phosphonium-choline, a 31P NMR-visible analog of choline in which the trimethyl-ammonium group of choline has been replaced with a trimethyl-phosphonium moiety. As shown previously [Sim et al. Biochem. J. 154, 303 (1976)], this compound is non-toxic and readily metabolized by cultured cells into phospholipids. In this paper we describe in greater detail some of the chemical and NMR spectroscopic properties of this material. Most significantly we show here that the chemical shift of phosphonium-choline is sensitive to the phosphorylation state of the analog and that the phosphonium nucleus is NMR-visible even after its incorporation into phospholipid. The unique properties of this analog should make it possible to use high-field 31P NMR to follow the flux of phosphonium-choline through the Kennedy pathway in intact perfused cells cultures.
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6
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Kaplan D, Boron W. Long-term expression of c-H-ras stimulates Na-H and Na(+)-dependent Cl-HCO3 exchange in NIH-3T3 fibroblasts. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)41751-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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7
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Swallow CJ, Grinstein S, Sudsbury RA, Rotstein OD. Relative roles of Na+/H+ exchange and vacuolar-type H+ ATPases in regulating cytoplasmic pH and function in murine peritoneal macrophages. J Cell Physiol 1993; 157:453-60. [PMID: 8253856 DOI: 10.1002/jcp.1041570304] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Two distinct mechanisms have been shown to mediate cytoplasmic pH (pHi) recovery in acid-loaded peritoneal macrophages (M phi s): Na+/H+ exchange and H+ extrusion by vacuolar-type (V-type) H+ ATPases. The present studies examined the relative roles of these two systems in maintaining pHi and cell function. Measurements of M phi pHi and superoxide (O2-) production in response to stimulation with 12-O-tetradecanoyl phorbol 13-acetate (TPA) were made at physiological or acidic extracellular pH (pHo) levels. The V-type H+ ATPase inhibitor, bafilomycin A1, and the potent Na+/H+ exchange inhibitor, N-ethyl-N-propylamino amiloride (EPA), were used to examine the contributions of these ion transporters to pHi regulation and cell function. At pHo 7.35, the complementary activities of the Na+/H+ antiport and the V-type H+ ATPase mediate pHi homeostasis. At pHo 6.7, maintenance of pHi depends primarily on H+ ATPase activity: bafilomycin A1 reduced pHi from 6.8 +/- 0.02 in control cells to 6.59 +/- 0.01 (P < 0.01) while EPA was without effect. The functional importance of V-type H+ ATPase-activity in preserving pHi homeostasis at acidic extracellular pH levels was reflected by the impairment of O2- production at pHo 6.70 when H+ ATPase activity was inhibited: bafilomycin A1 reduced O2- production from 13.9 +/- 1.0 to 9.3 +/- 0.6 nmoles/10(6) cells/40 min, in control and bafilomycin A1-treated cells, respectively (P < 0.05), while EPA had no effect. In subsequent studies, pHi was independently manipulated using the ionophore nigericin. Lowering pHi from 6.80 to 6.60 reduced O2- production from 15.3 +/- 1.8 to 9.8 +/- 1.6 nmoles/10(6) cells/40 min (P < 0.05), indicating that the cytoplasmic acidification resulting from inhibition of H+ ATPases at low pHo could account for the associated impairment of O2- production. In a more profoundly acidic environment (pHo 6.35), H+ ATPases remained active in regulating pHi, but could not preserve a sufficiently physiological pHi to support respiratory burst activity. V-type H+ ATPases constitute the dominant mechanism by which the pHi of peritoneal M phi s is maintained in an acidic extracellular environment.
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Affiliation(s)
- C J Swallow
- Department of Surgery, Toronto General Hospital, Canada
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8
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Wahl M, Gruenstein E. Intracellular free Ca2+ in the cell cycle in human fibroblasts: transitions between G1 and G0 and progression into S phase. Mol Biol Cell 1993; 4:293-302. [PMID: 8485320 PMCID: PMC300927 DOI: 10.1091/mbc.4.3.293] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Intracellular free calcium ([Ca2+]i) has been proposed to play an important part in the regulation of the cell cycle. Although a number of studies have shown that stimulation of quiescent cells with growth factors causes an immediate rise in [Ca2+]i (Rabinovitch et al., 1986; Vincentini and Villereal, 1986; Hesketh et al., 1988; Tucker et al., 1989, Wahl et al., 1990), a causal relationship between the [Ca2+]i transient and the ability of the cells to reenter the cell cycle has not been firmly established. We have found that blocking the mitogen-induced elevation of [Ca2+]i with the cytoplasmic [Ca2+]i buffer dimethyl BAPTA (dmBAPTA) also blocks subsequent entry of cells into S phase. The dose response curves for inhibition of serum stimulation of [Ca2+]i and DNA synthesis by dmBAPTA are virtually identical including an anomalous stimulation observed at low levels of dmBAPTA. Reversal of the [Ca2+]i buffering effect of dmBAPTA by transient exposure of the cells to the Ca2+ ionophore ionomycin also reverses the inhibition of DNA synthesis 20-24 h later. Ionomycin by itself does not stimulate DNA synthesis. These data are consistent with the conclusion that a transient increase in [Ca2+]i occurring shortly after serum stimulation of quiescent fibroblasts is necessary but not sufficient for subsequent entry of the cells into S phase. This study is the first to show a direct relationship between early serum stimulated Cai2+ increase and subsequent DNA synthesis in human cells. It also goes beyond recent studies on BALB/3T3 cells by providing dose response data and demonstrating reversibility, which are strong indications of a cause and effect relationship.
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Affiliation(s)
- M Wahl
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Ohio 45267-0524
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Gillies RJ, Galons JP, McGovern KA, Scherer PG, Lien YH, Job C, Ratcliff R, Chapa F, Cerdan S, Dale BE. Design and application of NMR-compatible bioreactor circuits for extended perfusion of high-density mammalian cell cultures. NMR IN BIOMEDICINE 1993; 6:95-104. [PMID: 8457432 DOI: 10.1002/nbm.1940060115] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
MR spectroscopy of cultured cells allows non-invasive analyses of the metabolism of cells with specific phenotypes under defined conditions. This technique can be used to investigate the intracellular metabolism of cells or extended to critically evaluate phenomena observed by in vivo MRS. In this paper, a cell maintenance system is described which allows MR analyses with unparalleled spectral resolution, S/N and stability. This system consists of a 25 mm diameter hollow fiber bioreactor and a supporting circuit. The hollow fiber reactor was chosen because it yields a large filling factor which can be perfused through defined volumes. The fibers were 300 microns diameter microporous (0.2 micron) cellulose acetate/cellulose nitrate membranes with high porosity, which allow bulk convective flow throughout the extracapillary space. This flow (Starling flow) is necessary to disrupt steady-state gradients in substrates and waste products. In many respects, the design of the supporting circuit is more important than the bioreactor itself, since it provides the reactor with the proper chemical and physical environment. Hence, this circuit can be applied to a variety of bioreactor configurations. The circuit consists of a hollow fiber oxygenator and a bleed-and-feed system housed in a temperature-controlled cabinet. Culture of mammalian cells in this reactor yields 31P spectra which have excellent spectral and temporal resolution. At confluence, endogenous 31P line widths were typically < 10 Hz (at 162 MHz) and well resolved spectra were obtained in < 30 s.
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Affiliation(s)
- R J Gillies
- Biological Magnetic Resonance Center, University of Arizona Health Sciences Center, Tucson 85724
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Kahn AM, Bishara M, Cragoe EJ, Allen JC, Seidel CL, Navran SS, O'Neil RG, McCarty NA, Shelat H. Effects of serotonin on intracellular pH and contraction in vascular smooth muscle. Circ Res 1992; 71:1294-304. [PMID: 1423928 DOI: 10.1161/01.res.71.6.1294] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Serotonin (5-HT) and other contractile agonists stimulate Na(+)-H+ exchange in vascular smooth muscle. Since intracellular alkalinization, per se, stimulates contraction, we tested whether 5-HT-induced contraction was associated with an increased pHi. In HCO3(-)-free buffer (pHo 7.4), 5-HT (10(-5) M) increased pHi, as measured by 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein fluorescence, from 7.10 +/- 0.03 to 7.34 +/- 0.03 (p < 0.01) in primary cultures of canine femoral artery vascular smooth muscle cells grown to confluence in the presence of 10% fetal calf serum. In HCO3- buffer (24 mM, pHo 7.4), resting pHi was 7.26 +/- 0.04 (p < 0.01 versus HCO3(-)-free buffer) but was not altered by 5-HT. In both types of buffer, 5-HT stimulated 5-(N-ethyl-N-isopropyl)amiloride-sensitive 22Na+ uptake (Na(+)-H+ exchange). In HCO3- buffer and in Na(+)- and HCO3(-)-free buffer, 5-HT increased 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid-sensitive 36Cl- uptake, suggesting that 5-HT stimulated Na(+)-independent Cl(-)-HCO3- and Cl(-)-Cl- exchange activities, respectively. Individual vascular smooth muscle cells were then cultured on rat tail tendon collagen gels in the presence of 0.5% fetal calf serum, and cell length and pHi were measured by video and epifluorescence microscopy. 5-HT contracted cells in a dose-dependent, reversible, and ketanserin-inhibitable manner. These cells, like cells grown in 10% fetal calf serum, exhibited Na(+)-H+ and Na(+)-independent Cl(-)-HCO3- exchange. In HCO3- buffer, 5-HT contracted cells without an associated change in pHi. We concluded the following: 1) 5-HT stimulated both Na(+)-H+ and Na(+)-independent Cl(-)-HCO3- exchange activities in cultured vascular smooth muscle cells in parallel. 2) As a result of enhanced H+ and HCO3- efflux, pHi was not altered. 3) In the presence of HCO3-, 5-HT-induced contraction was not associated with a change in pHi.
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MESH Headings
- 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid
- 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid/analogs & derivatives
- 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid/pharmacology
- Amiloride/analogs & derivatives
- Amiloride/pharmacology
- Animals
- Bicarbonates/metabolism
- Cells, Cultured
- Chlorides/metabolism
- Dogs
- Female
- HEPES/pharmacology
- Hydrogen-Ion Concentration
- Male
- Muscle Contraction/drug effects
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Serotonin/pharmacology
- Sodium/metabolism
- Stimulation, Chemical
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Affiliation(s)
- A M Kahn
- Department of Internal Medicine, University of Texas Medical School, Houston 77225
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11
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Alvarez LJ, Candia OA, Wolosin JM. Evidence for parallel Na(+)-H+ and Na(+)-dependent Cl(-)-HCO3- exchangers in cultured bovine lens cells. Exp Eye Res 1992; 55:747-55. [PMID: 1335884 DOI: 10.1016/0014-4835(92)90179-v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BCECF, a cell-entrapable dye with a pH-sensitive fluorescence spectrum, was used to identify transport mechanisms contributing to pH homeostasis of cultured bovine lens epithelial cells. Cells from a spontaneously established lineage were grown on glass coverslips that fit diagonally in a standard curvette and intracellular pH (pHi) was measured. Under perfusion with a CO2-HCO3(-)-free medium (pH 7.45), pHi was 7.19 +/- 0.21 (mean +/- S.D., n = 94 cell preparations). Cell acidifications (pHi to 6.65, n = 8) induced by the 'NH(4+)-loading' method were rapidly followed by a Na(+)-dependent, amiloride-inhibitable pHi recovery. Introduction of a CO2-HCO3(-)-rich medium (pH 7.45) resulted in a small acidification (0.18 +/- 0.04 U, n = 16; P < 0.002) due to rapid CO2 entry and an ensuing slow alkalinization to a pHi near the control CO2-HCO3(-)-free value. Subsequent removal of Cl- resulted in a further alkalinization of 0.18 +/- 0.02 U (n = 13; P < 0.001). This Cl- effect was completely inhibited by the absence of Na+, but was insensitive to amiloride, suggesting the presence of a Na(+)-dependent Cl(-)-HCO3- exchanger. Consistent with this posit, the reintroduction of Na+ to cells perfused in the absence of the cation with a HCO3(-)-containing, amiloride-complemented solution resulted in a gradual recovery from the acidic pHi induced by the baseline conditions (n = 6). The amiloride-insensitive, Na(+)- and HCO3(-)-dependent recovery was completely inhibited in cells pre-incubated with DIDS.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L J Alvarez
- Department of Ophthalmology, Mount Sinai School of Medicine, New York, NY 10029
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12
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Abstract
The literature describing 31P, 1H, 13C, 23Na and 19F MRS in vivo in human cancers is reviewed. Cancers have typical metabolic characteristics in 31P and 1H MRS including high levels of phospholipid metabolites and a cellular pH more alkaline than normal. These alone are not specific for cancer but are diagnostic in appropriate clinical settings. Some metabolic characteristics appear to be prognostic indices and correlation with treatment response is emerging as an important potentially cost-effective use of MRS in oncology. 19F MRS examines pharmacokinetics of 5-fluorouracil and by demonstrating its retention predicts response of a cancer to treatment. Current needs include improvement of diagnostic specificity by use of techniques like multivoxel MRS, proton decoupling of 31P, short echo time and fat-suppressed 1H MRS, 13C MRS direct or via 1H-observe, and statistical analysis of multiple spectral features. Trials in large populations in well defined clinical settings are needed to determine if MRS can provide independent prognostic indices useful in cancer management.
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Affiliation(s)
- W Negendank
- Department of NMR and Medical Spectroscopy, Fox Chase Cancer Center, Philadelphia, PA 19111
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13
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Navon G, Kushnir T, Askenasy N, Kaplan O. Two-Dimensional 31P-1H Correlation Spectroscopy in Intact Organs and Their Extracts. IN-VIVO MAGNETIC RESONANCE SPECTROSCOPY II: LOCALIZATION AND SPECTRAL EDITING 1992. [DOI: 10.1007/978-3-642-77208-5_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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14
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Kaplan O, van Cohen PCM, Cohen JS. NMR Studies of Metabolism of Cells and Perfused Organs. IN-VIVO MAGNETIC RESONANCE SPECTROSCOPY III: IN-VIVO MR SPECTROSCOPY: POTENTIAL AND LIMITATIONS 1992. [DOI: 10.1007/978-3-642-77218-4_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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15
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Gillies RJ, Martinez-Zaguilan R, Martinez GM, Serrano R, Perona R. Tumorigenic 3T3 cells maintain an alkaline intracellular pH under physiological conditions. Proc Natl Acad Sci U S A 1990; 87:7414-8. [PMID: 2170979 PMCID: PMC54757 DOI: 10.1073/pnas.87.19.7414] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
One of the earliest events in the response of mammalian cells to mitogens is activation of Na+/H+ exchange, which increases intracellular pH (pHin) in the absence of HCO3- or at external pH values below 7.2. The proliferative response can be blocked by preventing the pHin increase; yet, the proliferative response cannot be stimulated by artificially raising pHin with weak bases or high medium pH. These observations support the hypothesis that optimal pHin is a necessary, but not sufficient, component of the proliferative-response sequence. This hypothesis has recently been challenged by the observation that transfection of NIH 3T3 cells with yeast H(+)-ATPase renders them tumorigenic. Although previous measurements indicated that these transfected cells maintain a higher pHin in the absence of HCO3-, whether H(+)-ATPase transfection raised the pHin under physiologically relevant conditions was not known. The current report shows that these transfected cells do maintain a higher pHin than control cells in the presence of HCO3-, supporting the possibility that elevated pHin is a proliferative trigger in situ. We also show that these cells are serum-independent for growth and that they glycolyze much more rapidly than phenotypically normal cells.
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Affiliation(s)
- R J Gillies
- Department of Biochemistry, University of Arizona Health Sciences Center, Tucson 85724
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16
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Transformation and pH homeostasis of fibroblasts expressing yeast H(+)-ATPase containing site-directed mutations. Mol Cell Biol 1990. [PMID: 2142513 DOI: 10.1128/mcb.10.8.4110] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mouse fibroblasts expressing a yeast proton-pumping ATPase show tumorigenic transformation (R. Perona, and R. Serrano, Nature (London) 334:438-440, 1988). By expressing site-directed mutations of the yeast ATPase with different levels of activity, a close correlation has been found between enzyme activity, tumorigenic transformation, and intracellular pH measured by weak-acid distribution. Fibroblasts expressing the yeast proton-pumping ATPase showed increased capability to grow at acidic pH and to resist lethal acidification mediated by reversal of the Na(+)-H+ antiporter. Measurements with microelectrodes in individual cells demonstrated electrical hyperpolarization and confirmed the increased pH of cells expressing yeast ATPase. These results indicate that the yeast enzyme expressed in mouse fibroblasts has electrogenic proton-pumping activity and that this activity deregulates fibroblast growth. This suggests a connection between the biophysical phenomena of proton transport, intracellular pH, and membrane potential and the biochemical regulatory circuits based on protein kinases and transcription factors.
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17
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Perona R, Portillo F, Giraldez F, Serrano R. Transformation and pH homeostasis of fibroblasts expressing yeast H(+)-ATPase containing site-directed mutations. Mol Cell Biol 1990; 10:4110-5. [PMID: 2142513 PMCID: PMC360931 DOI: 10.1128/mcb.10.8.4110-4115.1990] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Mouse fibroblasts expressing a yeast proton-pumping ATPase show tumorigenic transformation (R. Perona, and R. Serrano, Nature (London) 334:438-440, 1988). By expressing site-directed mutations of the yeast ATPase with different levels of activity, a close correlation has been found between enzyme activity, tumorigenic transformation, and intracellular pH measured by weak-acid distribution. Fibroblasts expressing the yeast proton-pumping ATPase showed increased capability to grow at acidic pH and to resist lethal acidification mediated by reversal of the Na(+)-H+ antiporter. Measurements with microelectrodes in individual cells demonstrated electrical hyperpolarization and confirmed the increased pH of cells expressing yeast ATPase. These results indicate that the yeast enzyme expressed in mouse fibroblasts has electrogenic proton-pumping activity and that this activity deregulates fibroblast growth. This suggests a connection between the biophysical phenomena of proton transport, intracellular pH, and membrane potential and the biochemical regulatory circuits based on protein kinases and transcription factors.
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Affiliation(s)
- R Perona
- Instituto de Investigaciones Biomedicas, Madrid, Spain
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18
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Ingber DE, Prusty D, Frangioni JV, Cragoe EJ, Lechene C, Schwartz MA. Control of intracellular pH and growth by fibronectin in capillary endothelial cells. J Cell Biol 1990; 110:1803-11. [PMID: 2159481 PMCID: PMC2200182 DOI: 10.1083/jcb.110.5.1803] [Citation(s) in RCA: 208] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The aim of this work was to analyze the mechanism by which fibronectin (FN) regulates capillary endothelial cell proliferation. Endothelial cell growth can be controlled in chemically-defined medium by varying the density of FN coated on the substratum (Ingber, D. E., and J. Folkman. J. Cell Biol. 1989. 109:317-330). In this system, DNA synthetic rates are stimulated by FN in direct proportion to its effect on cell extension (projected cell areas) both in the presence and absence of saturating amounts of basic FGF. To investigate direct growth signaling by FN, we carried out microfluorometric measurements of intracellular pH (pHi), a cytoplasmic signal that is commonly influenced by soluble mitogens. pHi increased 0.18 pH units as FN coating densities were raised and cells progressed from round to spread. Intracellular alkalinization induced by attachment to FN was rapid and followed the time course of cell spreading. When measured in the presence and absence of FGF, the effects of FN and FGF on pHi were found to be independent and additive. Furthermore, DNA synthesis correlated with pHi for all combinations of FGF and FN. Ethylisopropylamiloride, a specific inhibitor of the plasma membrane Na+/H+ antiporter, completely suppressed the effects of FN on both pHi and DNA synthesis. However, cytoplasmic pH per se did not appear to be a critical determinant of growth since DNA synthesis was not significantly inhibited when pHi was lowered over the physiological range by varying the pH of the medium. We conclude that FN and FGF exert their growth-modulating effects in part through activation of the Na+/H+ exchanger, although they appear to trigger this system via separate pathways.
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Affiliation(s)
- D E Ingber
- Surgical Research Laboratory, Children's Hospital, Boston, Massachusetts
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Chapter 10 Regulation and Functional Significance of Cytoplasmic pH in Phagocytic Leukocytes. ACTA ACUST UNITED AC 1990. [DOI: 10.1016/s0070-2161(08)60082-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Stimulation of the Na+/H+ exchanger in human endothelial cells activated by granulocyte- and granulocyte-macrophage-colony-stimulating factor. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)51460-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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