Pyridine nucleotide distributions and enzyme mass action ratios in hepatocytes from fed and starved rats

Tischler, Marc E.; Friedrichs, Dagmar; Coll, Kathleen E.; Williamson, John

doi:10.1016/0003-9861(77)90346-0

Cited by 200 publications

(109 citation statements)

References 34 publications

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“…Regarding the absolute intramitochondrial concentrations of ketone bodies, our results agree with those of Tischler et al [30], amounting to 3-5 m M in the absence and presence of oleate, respectively. Moreover, these authors also noticed no concentration gradient between the cytosol and the extracellular medium, yet the value for the gradient between the cytosolic and mitochondrial compartments was even higher than that described herein.…”

Section: Subcehlur Distribution Of Ketone Bodiessupporting

confidence: 92%

“…In support of this is the fact that the cytosolic concentration of acetoacetate of 0.6-1 mM (see Fig.4B) is around the K , reported for acetoacetate transport of 0.6 mM [34]. Moreover, the intramitochondrial concentration of acetoacetate is higher by a factor of about 2 than that calculated [35] for a mere distribution according to the pH difference of 0.4 [17, 30,36] between the mitochondrial and cytosolic spaces. This is the more noteworthy, as 3-hydroxybutyrate under all conditions tested has been found to be distributed (see Fig.…”

Section: Subcehlur Distribution Of Ketone Bodiessupporting

confidence: 56%

“…Thus, the situation under our conditions is the inverse of that described by Demaugre et al [31]. The reason(s) for this cannot be given but may be related to the lack of information on methodological details [311 and the low number of experimental reproductions [30]. Nevertheless, these findings indicate that the widely accepted view that [3-hydroxybutyrate]/[acetoacetate] ratios in the whole liver reflect the mitochondrial redox state [29,32] can no longer be considered as generally applicable as hitherto assumed.…”

Section: Subcehlur Distribution Of Ketone Bodiesmentioning

confidence: 69%

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Role of Free Oxaloacetate in Ketogenesis. Derivation from the Direct Measurement of Mitochondrial [3-Hydroxybutyrate]/[Acetoacetate] Ratio in Hepatocytes

1982

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The distribution of ketone bodies between the cytosolic and mitochondrial spaces of isolated hepatocytes from 48-h-starved rats incubated at oleate concentrations of 0-0.8 mM has been investigated with respect to the rclationship between free mitochondrial oxaloacetate and the rate of ketone body formation.of the total cellular 3-hydroxybutyrate was found to be located intramitochondrially, independent of the oleate concentration used. Acetoacetate, however, was almost equally distributed between the two compartments. In contrast to acetoacetate, 3-hydroxybutyrate distribution followed the transmitochondrial pH gradient.2. The mitochondrial concentrations of 3-hydroxybutyrate and acetoacetate were higher (by a factor of about 2 and 4, respectively) than those in the cytosol. N o concentration gradient was found between the cytosol and the incubation medium. At 0.8 mM oleate the mitochondrial concentration of 3-hydroxybutyrate amounted to 4.5 i 0.6 niM (E = 9), the [3-hydroxybutyrate]/[acetoacetate] ratio being 1.4. Considerably higher values for this ratio resulted from the rate of ketone body production.3. Mitochondrial concentrations of malate were increased by oleate concentrations between 0.1 -0.8 mM, while mitochondrial concentrations of citrate were not significantly changed.4. Mitochondrial concentrations of free oxaloacetate calculated from the contents of malate and ketone bodies measured in the mitochondrial compartment was found to be correlated in an inverse manner with thc rate of ketone body production.5. The results are discussed with regard to the current concepts for the control of ketogenesis. Our data strongly support the classical view of the oxaloacetate concentration playing a key role in the regulation of production of ketone bodies. Some 25The current theories on the regulation of ketogenesis by the nyammalian liver under conditions of increased peripheral mobilisation of fatty acids, such as starvation and diabetes, are moving along two general lines. One is concerncd with the regulation of the transport of fatty acids into the mitochondria as fuel for P-oxidation and acetyl-CoA production [I -41, while the other focuses attention on the disposal of acetylCoA by the citric acid cycle and the ketogenic pathway, respectively (for review see [5 -71). The pioneering experiments by Lehninger in 1946 [8] have initiated the proposal [9], that the availability of oxaloacetate for citrate synthase represents the major regulatory factor in ketogenesis. The present study is concerned with the latter hypothesis. Although a lot of evidence in favour of it has been accuniulated by studies with isolated mitochondria [lo, 3 11, the perfused rat liver (for review see [5]) and the intact rat [12,13] direct experimental proof is still lacking. This is due to the fact that the separate determination of mitochondrial metabolites in hepatocytes was not possible until Zuurendonk and This work is dedicated to Prof. Dr H. Holzcr on the occasion of his 60th birthday.Enzymes. Citrate synthase (EC 4.1.3.7); coll...

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Section: Subcehlur Distribution Of Ketone Bodiessupporting

confidence: 92%

Section: Subcehlur Distribution Of Ketone Bodiessupporting

confidence: 56%

Section: Subcehlur Distribution Of Ketone Bodiesmentioning

confidence: 69%

See 1 more Smart Citation

Role of Free Oxaloacetate in Ketogenesis. Derivation from the Direct Measurement of Mitochondrial [3-Hydroxybutyrate]/[Acetoacetate] Ratio in Hepatocytes

1982

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“…This conclusion is in agreement with measurements made of intracellular lactate and pyruvate concentrations in hepatocytes under conditions of rapid gluconeogenesis (Groen et al, 1983). Our data also confirm the widely held view that lactate, pyruvate, and the ketone bodies equilibrate across the liver cell plasma membrane, allowing extracellular lactate/pyruvate and ␤-hydroxybutyrate/acetoacetate ratios to be used to estimate cytosolic and mitochondrial NADH/NAD ϩ ratios, respectively (see Tischler et al (1977), Groen et al (1983), and Poole and Halestrap (1993) …”

supporting

confidence: 90%

The Kinetics, Substrate, and Inhibitor Specificity of the Monocarboxylate (Lactate) Transporter of Rat Liver Cells Determined Using the Fluorescent Intracellular pH Indicator, 2′,7′-Bis(carboxyethyl)-5(6)-carboxyfluorescein

Jackson¹,

Halestrap

1996

Journal of Biological Chemistry

173

129

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The kinetics of transport of L-lactate, pyruvate, ketone bodies, and other monocarboxylates into isolated hepatocytes from starved rats were measured at 25°C using the intracellular pH-sensitive dye, 2 ,7 -bis(carboxyethyl)-5(6)-carboxyfluorescein, to detect the associated proton influx. Transport kinetics were similar, but not identical, to those determined using the same technique for the monocarboxylate transporter (

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“…Glucose was determined using the glucose oxidase method [16] and both lactate [17] and pyruvate [18] were assayed in extracts of incubated whole cells. Previous studies have shown that similar ratios of lactate to pyruvate are found in the cytosol, whole cells, or the suspending medium [19,20]. Urea was measured in deproteinized extracts using urease and glutamate dehydrogenase…”

Section: Metabolite Determinationsmentioning

confidence: 99%

Quinolinate inhibition of gluconeogenesis is dependent on cytosolic oxalacetate concentration

Gabbay¹

1985

FEBS Letters

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In isolated rat hepatocytes, the phosphoenolpyruvate carboxykinase (PEPCK) inhibitor, quinolinate decreased gluconeogenesis from lactate more than from pyruvate (78 vs 44%). Quinolinate inhibition of PEPCK has been reported to be competitive with oxalacetate (OAA), and therefore higher cytosolic OAA concentrations could be expected to alleviate quinolinate inhibition of PEPCK and hence reduce its effect on gluconeogenesis. With pyruvate as a carbon source, the cytosolic concentration of OAA was higher than with lactate (40 vs 9.7 PM). The levels of OAA were manipulated metabolically by adding asparagine (which provides more cytosolic OAA through the urea cycle) or oleate (which increases malate efllux from the mitochondria). In each of the 8 conditions studied, quinolinate inhibition of gluconeogenesis was inversely related to the levels of OAA in the cytosol. Quinolinate inhibition of asparagine gluconeogenesis was not due to a non-specific effect on urea synthesis. Gluconeogenesis Rat hepatocyte Quinolinate Phosphoenolpyruvate carboxykinase AsparagineOxalocetate

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Pyridine nucleotide distributions and enzyme mass action ratios in hepatocytes from fed and starved rats

Cited by 200 publications

References 34 publications

Role of Free Oxaloacetate in Ketogenesis. Derivation from the Direct Measurement of Mitochondrial [3-Hydroxybutyrate]/[Acetoacetate] Ratio in Hepatocytes

Role of Free Oxaloacetate in Ketogenesis. Derivation from the Direct Measurement of Mitochondrial [3-Hydroxybutyrate]/[Acetoacetate] Ratio in Hepatocytes

The Kinetics, Substrate, and Inhibitor Specificity of the Monocarboxylate (Lactate) Transporter of Rat Liver Cells Determined Using the Fluorescent Intracellular pH Indicator, 2′,7′-Bis(carboxyethyl)-5(6)-carboxyfluorescein

Quinolinate inhibition of gluconeogenesis is dependent on cytosolic oxalacetate concentration

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