The relationship between mitochondrial state, ATP hydrolysis, [Mg2+]i and [Ca2+]i studied in isolated rat cardiomyocytes.

Leyssens, A; Nowicky, Alexander V.; Patterson, Linda; Crompton, Martin; Duchen, Michael R.

doi:10.1113/jphysiol.1996.sp021669

Cited by 206 publications

(209 citation statements)

References 39 publications

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“…Colonic crypts were incubated with Mg-Green (4μmol/L) for 60 minutes than were excited with 476nm light and emission was detected at 500-550nm. Because ATP has a 10-fold greater affinity for Mg 2+ than ADP, and most intracellular Mg 2+ is present as Mg-ATP [22,27], the ADP:ATP ratio can be monitored. The elevation of fluorescence intensity caused by the increase in free intracellular Mg 2+ concentration suggests a reduction of (ATP) i [7].…”

Section: Materials and Solutions For The Experimentsmentioning

confidence: 99%

Bile acids inhibit Na+/H+ exchanger and Cl−/HCO3 − exchanger activities via cellular energy breakdown and Ca2+ overload in human colonic crypts

Pallagi-Kunstár

Farkas

Maléth

et al. 2014

Pflugers Arch - Eur J Physiol

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Abstract:Bile acids play important physiological role in the solubilisation and absorption of dietary lipids. However, under pathophysiological conditions, such as short bowel syndrome, they can reach the colon in high concentrations inducing diarrhea. In this study our aim was to characterise the cellular pathomechanism of bile-induced diarrhea using human samples. Colonic crypts were isolated from biopsies of patients (controls with negative colonoscopic findings) and of cholecystectomised/ileumresected patients with or without diarrhoea. In vitro measurement of the transporter activities revealed impaired Na+/H+ exchanger (NHE) and Cl-/HCO3-exchanger (CBE) activities in cholecystectomised/ileum-resected patients suffering from diarrhea, compared to control patients. Acute treatment of colonic crypts with 0.3mM chenodeoxycholate caused dose-dependent intracellular acidosis; moreover, the activities of acid/base transporters (NHE and CBE) were strongly impaired. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 3 AbstractBile acids play important physiological role in the solubilisation and absorption of dietary lipids. However, under pathophysiological conditions, such as short bowel syndrome, they can reach the colon in high concentrations inducing diarrhea. In this study our aim was to characterise the cellular pathomechanism of bile-induced diarrhea using human samples. Colonic crypts were isolated from biopsies of patients (controls with negative colonoscopic findings) and of cholecystectomised/ileum-resected patients with or without diarrhoea. In vitro measurement of the transporter activities revealed impaired Na + /H + exchanger (NHE) and Cl -/HCO 3 -exchanger (CBE) activities in cholecystectomised/ileum-resected patients suffering from diarrhea, compared to control patients. Acute treatment of colonic crypts with 0.3mM chenodeoxycholate caused dose-dependent intracellular acidosis; moreover, the activities of acid/base transporters (NHE and CBE) were strongly impaired. This concentration of chenodeoxycholate did not cause morphological changes in colonic epithelial cells, although significantly reduced the intracellular ATP level, decreased mitochondrial transmembrane potential and caused sustained intracellular Ca 2+ elevation. We also showed that chenodeoxycholate induced Ca 2+ release from the endoplasmic reticulum and extracellular Ca 2+ influx contributing to the Ca 2+ elevation. Importantly, our results suggest that the chenodeoxycholate induced inhibition of NHE activities was ATP-dependent, whereas the inhibition of CBE activity was mediated by the sustained Ca 2+ elevation.We suggest that bile acids inhibit the function of ion transporters via cellular energy breakdown and Ca 2+ overload in human colonic epithelial cells, which can reduce fluid and electrolyte absorption in the colon and promote ...

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Section: Materials and Solutions For The Experimentsmentioning

confidence: 99%

Bile acids inhibit Na+/H+ exchanger and Cl−/HCO3 − exchanger activities via cellular energy breakdown and Ca2+ overload in human colonic crypts

Pallagi-Kunstár

Farkas

Maléth

et al. 2014

Pflugers Arch - Eur J Physiol

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“…ATP has a greater affinity than ADP for Mg 2ϩ (13,14). Therefore, as intracellular ATP increases, the cytosolic ionized Mg 2ϩ concentration falls, reflected by a reduction in fluorescence intensity in cells loaded with MgG.…”

Section: Methodsmentioning

confidence: 99%

“…The first technique involved the measurement of Magnesium Green fluorescence in islets. This method of measuring ATP takes advantage of the fact that ATP has a greater affinity for Mg 2ϩ than ADP so that the intracytoplasmic [Mg 2ϩ ] decreases when ATP is formed (13,14). Using this technique, we have demonstrated a significantly smaller decrease in MgG fluorescence intensity in (Ϫ/Ϫ) islets compared with control islets in response to glucose stimulation, thus providing indirect evidence to support the hypothesis that there is a defect in ATP generation in response to glucose in HNF-1␣ (Ϫ/Ϫ) islets.…”

Section: ␤-Cell Glycolytic Signaling In Mice Lacking Hnf-1␣mentioning

confidence: 99%

Defective Pancreatic β-Cell Glycolytic Signaling in Hepatocyte Nuclear Factor-1α-deficient Mice

Dukes¹,

Sreenan²,

Roe³

et al. 1998

Journal of Biological Chemistry

153

113

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Mutations in the hepatocyte nuclear factor-1␣ (HNF-1␣] i , and corrected the insulin secretion defect. NAD(P)H responses to glucose were substantially reduced, and inhibitors of glycolytic NADH generation reproduced the mutant phenotype in normal islets. Flux of glucose through glycolysis in islets from mutant mice was reduced, as a result of which ATP generation in response to glucose was impaired. We conclude that hepatocyte nuclear factor-1␣ diabetes results from defective ␤-cell glycolytic signaling, which is potentially correctable using substrates that bypass the defect.

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“…Nucleotides were eluted with a linear gradient of triethylammonium bicarbonate buffer (4,20). In addition, changes in ATP levels in intact cells were determined by measuring free Mg 2ϩ concentration using the fluorescent indicator Magnesium Green (23). This technique, validated for assessment of ATP levels in cardiomyocytes, is based on the greater affinity of Mg 2ϩ for ATP than ADP, resulting in an increase in cytosolic Mg 2ϩ concentration upon ATP hydrolysis (23).…”

Section: Methodsmentioning

confidence: 99%

Energetic communication between mitochondria and nucleus directed by catalyzed phosphotransfer

Dzeja

Bortolon

Perez‐Terzic

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

146

121

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Exchange of information between the nucleus and cytosol depends on the metabolic state of the cell, yet the energy-supply pathways to the nuclear compartment are unknown. Here, the energetics of nucleocytoplasmic communication was determined by imaging import of a constitutive nuclear protein histone H1. Translocation of H1 through nuclear pores in cardiac cells relied on ATP supplied by mitochondrial oxidative phosphorylation, but not by glycolysis. Although mitochondria clustered around the nucleus, reducing the distance for energy transfer, simple nucleotide diffusion was insufficient to meet the energetic demands of nuclear transport. Rather, the integrated phosphotransfer network was required for delivery of high-energy phosphoryls from mitochondria to the nucleus. In neonatal cardiomyocytes with low creatine kinase activity, inhibition of adenylate kinase-catalyzed phosphotransfer abolished nuclear import. With deficient adenylate kinase, nucleoside diphosphate kinase, which secures phosphoryl exchange between ATP and GTP, was unable to sustain nuclear import. Up-regulation of creatine kinase phosphotransfer, to mimic metabolic conditions of adult cardiac cells, rescued H1 import, suggesting a developmental plasticity of the cellular energetic system. Thus, mitochondrial oxidative phosphorylation coupled with phosphotransfer relays provides an efficient energetic unit in support of nuclear transport. E fficient communication between the cytosol and nucleus is essential in cellular homeostasis, regulating proper processing of genetic and metabolic information. Central in nucleocytoplasmic exchange is the transport of macromolecules across the nuclear envelope (1, 2), a multistep process that initially proceeds by signal-mediated recognition of the macromolecule to be transported, following by docking events and, ultimately, translocation through nuclear pores (1-5). In energy-depleted cells, molecules that are actively transported into the nucleus, such as the constitutive chromatin protein histone H1, tend to accumulate on the cytosolic surface of the nuclear membrane (2, 4). While formation and docking of the transported protein, complexed with a transport receptor, may be energy-independent, the actual translocation and accumulation of molecules in the nuclear compartment against a concentration gradient may, however, require an energy source (4).Energy-consuming enzymes, including nucleoside triphosphatases, are associated with the nuclear envelope, and their activity is stimulated in the presence of the transported substrate (6, 7). Underscoring the energetic cost of nuclear transport, receptor cycling and continued signal processing mandate catalytic conversion of the guanine nucleotide-binding protein Ran from Ran-GTP to Ran-GDP, which is accomplished by the RanGTPase and the subsequent regeneration of GTP (1, 2). Yet, transport of macromolecules across the nuclear envelope that can proceed in an apparently energy-independent manner also has been reported (8, 9). This observation was, however, made i...

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The relationship between mitochondrial state, ATP hydrolysis, [Mg2+]i and [Ca2+]i studied in isolated rat cardiomyocytes.

Abstract: 1. As ATP has a higher affinity for Mg2+ than ADP, the cytosolic magnesium concentration rises upon ATP hydrolysis. We have therefore used the Mg2+-sensitive fluorescent indicator Magnesium Green (MgG)

Cited by 206 publications

References 39 publications

Bile acids inhibit Na+/H+ exchanger and Cl−/HCO3 − exchanger activities via cellular energy breakdown and Ca2+ overload in human colonic crypts

Bile acids inhibit Na+/H+ exchanger and Cl−/HCO3 − exchanger activities via cellular energy breakdown and Ca2+ overload in human colonic crypts

Defective Pancreatic β-Cell Glycolytic Signaling in Hepatocyte Nuclear Factor-1α-deficient Mice

Energetic communication between mitochondria and nucleus directed by catalyzed phosphotransfer

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