The influence of fructose and its metabolites on ethanol metabolism <i>in vitro</i>

Thieden, H. I. D.; Lundquist, Frank

doi:10.1042/bj1020177

Cited by 62 publications

(15 citation statements)

References 19 publications

(12 reference statements)

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“…I n accordance with this view, the cytosolic NADH/NAD+ ratio is decreased in ethanolmetabolizing liver slices after administration of fructose [30]. I n the perfused rat liver, the unstimulated ethanol oxidation rate is about twice that in the isolated rat-liver parenchymal cells (see above).…”

Section: Rate-limiting Steps In Ethanol Oxidation and The "Fructose Esupporting

confidence: 56%

“…The concentrations of pyrazole applied are so low that inhibition of enzymes other than the NAD-dependent alcohol dehydrogenase is improbable [14]. The results of Fig.2 may therefore be taken as evidence for the suggestion [30] that the NAD-dependent alcohol dehydrogenase is involved in the "fructose effect".…”

Section: Effect Of Fructose and Pyruvatementioning

confidence: 97%

“…The fully drawn graph of Fig. 1 represents the expected rate of ethanol oxidation assuming the rates measured a t 4, 10, 20, 30 and 40mM ethanol to reflect the combined action of two enzymes with the K, and V values mentioned above.…”

Section: Effect Of Ethanol Concentrationmentioning

confidence: 99%

“…unstimulated ethanol oxidation only 30 Ole, indicating that the "fructose effect" is mediated via alcohol deh y drogenase .…”

mentioning

confidence: 91%

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Rate‐Limiting Factors in Ethanol Oxidation by Isolated Rat‐Liver Parenchymal Cells

Grunnet¹,

Quistorff²,

Thieden³

1973

European Journal of Biochemistry

126

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1. Isolated rat-liver parenchymal cells oxidized ethanol a t a rate of 1.4, 1.7, i.9 and 2.5 p.mol/ min per ml packed cells at 4, 20, 40 and 65 mM ethanol, respectively. Between 40 and 65 mM ethanol an abrupt 30°/, increase in the ethanol oxidation rate was observed.2. The activity of the NAD-dependent alcohol dehydrogenase in a homogenate of isolated cells corresponded to 1.25-5 U/ml packed cells, depending on the assay method used.3. Fructose or pyruvate enhanced the oxidation rate of ethanol by 1.4-2.0 pmol/min per ml packed cells independent of the ethanol concentration applied. No additive effect of the two compounds upon ethanol oxidation was observed.4. Pyrazole inhibited the NAD dependent alcohol dehydrogenase activity in a homogenate of isolated cells as well as the unstimulated and the fructose-stimulated ethanol oxidation with a Ki-value of 9-13 pM.by pyrazole concentrations, which inhibited the unstimulated ethanol oxidation only 30 Ole, indicating that the "fructose effect" is mediated via alcohol deh y drogenase .4mM pyrazole only slightly inhibited that part of the ethanol oxidation which was not catalyzed by alcohol dehydrogenase, whereas 18 mM pyrazole inhibited also this pathway significantly. 5. 50 pM pyrazole had no effect a t all upon the basal ethanol oxidation rate whereas the fructose-stimulated ethanol oxidation was 30°/, inhibited.6. The results concerning the effect of fructose and pyruvate upon ethanol oxidation are interpreted in terms of the mechanism for the reaction catalyzed by alcohol dehydrogenase. At low concentrations of ethanol and in the absence of fructose, the rate-limiting step in ethanol oxidation appears to be dissociation of the enzyme-NADH complex, whereas, in the presence of fructose, the maximal activity of ethanol dehydrogenase may be rate-limiting for the oxidation of ethanol.7. The results also suggest that enzyme systems other than alcohol dehydrogenase participate in ethanol oxidation a t high concentrations of ethanol.The "fructose effect" was inhibited 100Three different reaction mechanisms for oxidation of ethanol to acetaldehyde have been described in liver tissue. These are the pathway catalyzed by the NAD-dependent alcohol dehydrogenase [ 11, the pathway involving hydrogen peroxide and catalase [2 -51 and the microsomal ethanol-oxidizing system involving NADPH and cytochrome P-450 [6-81. The pathway catalyzed by alcohol dehydrogenase is localized to the cytoplasmic compartment of the cell, while the system dependent on cytochrome P-450 is microsome-bound. Eur. J. Bioohem. 40 (1973) The oxidation of ethanol catalyzed by alcohol dehydrogenase, which prevails a t low (below approx.

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Section: Rate-limiting Steps In Ethanol Oxidation and The "Fructose Esupporting

confidence: 56%

Section: Effect Of Fructose and Pyruvatementioning

confidence: 97%

Section: Effect Of Ethanol Concentrationmentioning

confidence: 99%

“…unstimulated ethanol oxidation only 30 Ole, indicating that the "fructose effect" is mediated via alcohol deh y drogenase .…”

mentioning

confidence: 91%

See 2 more Smart Citations

Rate‐Limiting Factors in Ethanol Oxidation by Isolated Rat‐Liver Parenchymal Cells

Grunnet¹,

Quistorff²,

Thieden³

1973

European Journal of Biochemistry

126

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“…Fructose has been shown to increase the rate of hepatic ethanol oxidation in man and dog in vivo [1,2,3] in the catheterized human liver [4] on isolated parenchymal liver cells from rats [5] and on rat and human-liver slices [6,7]. The magnitude of this effect depends on the species.…”

mentioning

confidence: 99%

Metabolism of Ethanol and Fructose in the Isolated Perfused Pig Liver

Damgaard

Lundquist

Sestoft

et al. 1973

European Journal of Biochemistry

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1. Ethanol at concentrations below 10 mM was oxidized a t a rate of 0.7 pmol x g-1 x min-l by the perfused pig liver. Infusion of fructose caused a stimulation (up to 120°/,) of ethanol oxidation, which was proportional to the rate of fructose elimination.2. Stimulation was observed also when D-glyceraldehyde (a fructose metabolite) was used. Even a t high D-glyceraldehyde concentrations, the increase in ethanol metabolism was less than with fructose.3. Hepatic acetate metabolism was not affected by ethanol but was stimulated up to 1000/, by fructose in the presence of ethanol. 4.The concentration ratios of sorbitol/fructose and lactatelpyruvate in the perfusion medium were increased in experimental periods with ethanol and fructose compared to periods with fructose alone. The data indicate equilibrium between these metabolites and the free NADH/NAD in the cytosol.5. The steady-state concentrations of D-glyceraldehyde and glycerol were increased when ethanol was infused together with fructose, while the production of D-glycerate was reduced to zero.6. The rate of fructose elimination was not influenced by ethanol, although the output of lactate and glucose were diminished.7 . Accumulation of the reduced metabolites (sorbitol, glycerol, L-glycerol 3-phosphate) accounted for only a small part of the reducing equivalents generated during fructose-stimulated ethanol oxidation. Complete oxidation of the ethanol metabolized would require 3.6 pmol 0, x g-1 x min-l compared to a measured uptake of 1.8 pmol x g-l x min-1. As ketone bodies and acetaldehyde were not produced in significant amounts, the retained acetate must be used in syntheses, e.g. of fatty acids.

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Absorption, Diffusion, Distribution, and Elimination of Ethanol: Effects on Biological Membranes

Kalant

1971

The Biology of Alcoholism

120

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The influence of fructose and its metabolites on ethanol metabolism in vitro

Cited by 62 publications

References 19 publications

Rate‐Limiting Factors in Ethanol Oxidation by Isolated Rat‐Liver Parenchymal Cells

Rate‐Limiting Factors in Ethanol Oxidation by Isolated Rat‐Liver Parenchymal Cells

Metabolism of Ethanol and Fructose in the Isolated Perfused Pig Liver

Absorption, Diffusion, Distribution, and Elimination of Ethanol: Effects on Biological Membranes

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