A Comparison of Some Kinetic Properties of Soluble and Bound Lactate Dehydrogenase Isoenzymes at Different Temperatures

Nitisewojo, Poedijono; Hultin, Herbert O.

doi:10.1111/j.1432-1033.1976.tb10636.x

Cited by 41 publications

(6 citation statements)

References 42 publications

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“…This phenomenon was also observed with other enzymes upon their association with membranes and was attributed to a reduced accessibility of exogenous radioactive substrate to the enzyme and/or to a "dilution" effect on the exogenous radioactive substrate; i.e. the presence of endogenous membrane phospholipids lowered the effective specific activity of the radioactive substrate (57)(58)(59). The normal Ca 2ϩ concentration in endothelial cells is approximately 70 nM (60,61), and in the current study lyso-PC was found to cause a 3-fold increase in the intracellular Ca 2ϩ level.…”

Section: Lyso-pc-induced Arachidonate Release In Endothelial Cellsmentioning

confidence: 68%

Lysophosphatidylcholine Stimulates the Release of Arachidonic Acid in Human Endothelial Cells

Wong¹,

Tran²,

Pierce³

et al. 1998

Journal of Biological Chemistry

106

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Lysophosphatidylcholine (lyso-PC) is a product of phosphatidylcholine hydrolysis by phospholipase A 2 (PLA 2 ) and is present in cell membranes, oxidized lipoproteins, and atherosclerotic tissues. It has the ability to alter endothelial functions and is regarded as a causal agent in atherogenesis. In this study, the modulation of arachidonate release by lyso-PC in human umbilical vein endothelial cells was examined. Incubation of endothelial cells with lyso-PC resulted in an enhanced release of arachidonate in a time-and concentration-dependent manner. Maximum arachidonate release was observed at 10 min of incubation with 50 M lyso-PC. Lyso-PC species containing palmitoyl (C 16:0 ) or stearoyl (C 18:0 ) groups elicited the enhancement of arachidonate release, while other lysolipids such as lysophosphatidylethanolamine, lysophosphatidylserine, lysophosphatidylinositol, or lysophosphatidate were relatively ineffective. Lyso-PC-induced arachidonate release was decreased by treatment of cells with PLA 2 inhibitors such as para-bromophenacyl bromide and arachidonoyl trifluoromethyl ketone. Furthermore, arachidonate release was attenuated in cells grown in the presence of antisense oligodeoxynucleotides that specifically bind cytosolic PLA 2 mRNA. Treatment of cells with lyso-PC resulted in a translocation of PLA 2 activity from the cytosolic to the membrane fractions of cells. Lyso-PC induced a rapid influx of Ca 2؉ from the medium into the cells, with a simultaneous enhancement of protein kinase C (PKC) activity in the membrane fractions. The lyso-PC-induced arachidonate release was attenuated when cells were preincubated with specific inhibitors of PKC (staurosporine and Ro31-8220) or a specific inhibitor of mitogen-activated protein kinase/extracellular regulated kinase kinase (PD098059). Taken together, the results of this study show that lyso-PC caused the elevation of cellular Ca 2؉ and the activation of PKC, which stimulated cytosolic PLA 2 in an indirect manner and resulted in an enhanced release of arachidonate.

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Section: Lyso-pc-induced Arachidonate Release In Endothelial Cellsmentioning

confidence: 68%

Lysophosphatidylcholine Stimulates the Release of Arachidonic Acid in Human Endothelial Cells

Wong¹,

Tran²,

Pierce³

et al. 1998

Journal of Biological Chemistry

106

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“…LDH activity was measured according to the modified method of Bergmeyer as previously published . The LDH isoenzymes in the total extracts of neurons and glial cells were separated according to the method of polyacrylamide disc electrophoresis of Nitisewojo and Hultin (1976). The densitometric recordings were performed on a Vernon microdensitometer.…”

Section: Methodsmentioning

confidence: 99%

Activity and Isoenzyme Pattern of Lactate Dehydrogenase in Neurons and Astroblasts Cultured from Brains of Chick Embryos

Tholey

Roth-Schechter

Mandel

1981

Journal of Neurochemistry

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Primary cultures of neurons and glial cells (astroblasts) prepared from brains of 8-day-old and 15-day-old chick embryos, respectively, were grown for periods between 3 and 19 days. Specific activity of lactate dehydrogenase (LDH) increased in both types of cultures as a function of time and was always significantly higher in glial cells than in neurons. Glial cell extracts were found to contain predominantly the anaerobic isoenzymatic form of LDH (LDH-M4), and this pattern did not change over a period of 19 days. Cultured neurons contained predominantly the aerobic isoenzymatic form LDH-H4, and there was a progressive appearance of all other isoenzymes over an 8-day period. These results support the hypothesis of a different energy metabolism in neurons and glia.

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“…However, the free energy of a biochemical reaction determines its direction, not the enzyme catalyzing it (Lehninger et al, 1993), so the dominant presence of LDH-1 in neurons does not influence the direction of the LDH reaction. Also, the lower V max of LDH-1 can offset the effects of its lower K m when the enzyme activity of LDH-1 is compared with that of LDH-5 (Nitisewojo and Hultin, 1976). Of greater importance is that LDH-1 is more sensitive to pyruvate product inhibition (K i ‫ס‬ 0.18 mM for LDH-1 and 0.28 mM for LDH-5) (Stambaugh and Post, 1966).…”

Section: The Ldh Isoform Distributionmentioning

confidence: 99%

Energy Substrates for Neurons during Neural Activity: A Critical Review of the Astrocyte-Neuron Lactate Shuttle Hypothesis

Chih

Roberts

2003

J Cereb Blood Flow Metab

295

250

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Summary:Glucose had long been thought to fuel oxidative metabolism in active neurons until the recently proposed astrocyte-neuron lactate shuttle hypothesis (ANLSH) challenged this view. According to the ANLSH, activity-induced uptake of glucose takes place predominantly in astrocytes, which metabolize glucose anaerobically. Lactate produced from anaerobic glycolysis in astrocytes is then released from astrocytes and provides the primary metabolic fuel for neurons. The conventional hypothesis asserts that glucose is the primary substrate for both neurons and astrocytes during neural activity and that lactate produced during activity is removed mainly after neural activity. The conventional hypothesis does not assign any particular fraction of glucose metabolism to the aerobic or anaerobic pathways. In this review, the authors discuss the theoretical background and critically review the experimental evidence regarding these two hypotheses. The authors conclude that the experimental evidence for the ANLSH is weak, and that existing evidence and theoretical considerations support the conventional hypothesis. Key Words: Brain-Energy metabolismGlucose-Glycolysis-Lactate-Oxidative phosphorylation.Until recently, glucose had stood unchallenged as the principal metabolic substrate of the mature brain (for example, see McIlwain and Bachelard, 1985;Sokoloff, 1989). The primacy of glucose, though, has been questioned recently by some investigators who view lactate as a substrate that active neurons prefer over glucose (Magistretti, 1999; Magistretti et al., 1999). The brain can consume lactate as a substrate, as has been demonstrated by studies showing that the brain uses lactate during hypoglycemia or during periods of elevated blood lactate (Ide et al., 2000;Nemoto et al., 1974). Also, some in vitro studies have shown that lactate supports neural activity in brain tissues in the absence of glucose (e.g., Izumi et al., 1997;Schurr et al., 1988). However, because lactate does not pass through the blood-brain barrier nearly as well as glucose (e.g., McIlwain and Bachelard, 1985), lactate cannot serve the brain as a bloodborne substrate the way glucose does. In the mid 1990s, an astrocyte-neuron lactate shuttle hypothesis (ANLSH) was proposed that assigned a major metabolic role to brain-derived lactate (Pellerin and Magistretti, 1994;Tsacopoulos and Magistretti, 1996). According to this hypothesis, lactate is produced in an activity-dependent and glutamate-mediated manner by astrocytes and is then transferred to and used by active neurons (Pellerin et al., 1998a). In greater detail, the ANLSH postulates that neuronal activation increases the extracellular concentration of brain glutamate, which astrocytes take up via high affinity, Na + -dependent transporters. Increases in glutamate and Na + in astrocytes activate glutamine synthetase and Na + -K + ATPase, respectively. Activation of Na + -K + ATPase spurs astrocytic ATP consumption. This leads to activation of anaerobic glycolysis 1 in astrocytes, and the resulting lactat...

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A Comparison of Some Kinetic Properties of Soluble and Bound Lactate Dehydrogenase Isoenzymes at Different Temperatures

Cited by 41 publications

References 42 publications

Lysophosphatidylcholine Stimulates the Release of Arachidonic Acid in Human Endothelial Cells

Lysophosphatidylcholine Stimulates the Release of Arachidonic Acid in Human Endothelial Cells

Activity and Isoenzyme Pattern of Lactate Dehydrogenase in Neurons and Astroblasts Cultured from Brains of Chick Embryos

Energy Substrates for Neurons during Neural Activity: A Critical Review of the Astrocyte-Neuron Lactate Shuttle Hypothesis

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