1. The subcellular distribution of adenine nucleotides, acetyl-CoA, CoA, glutamate, 2-oxoglutarate, malate, oxaloacetate, pyruvate, phosphoenolpyruvate, 3-phosphoglycerate, glucose 6-phosphate, aspartate and citrate was studied in isolated hepatocytes in the absence and presence of glucagon by using a modified digitonin procedure for cell fractionation. 2. In the absence of glucagon, the cytosol contains about two-thirds of cellular ATP, some 40–50% of ADP, acetyl-CoA, citrate and phosphoenolpyruvate, more than 75% of total 2-oxoglutarate, glutamate, malate, oxaloacetate, pyruvate, 3-phosphoglycerate and aspartate, and all of glucose 6-phosphate. 3. In the presence of glucagon the cytosolic space shows an increase in the content of malate, phosphoenolpyruvate and 3-phosphoglycerate by more than 60%, and those of aspartate and glucose 6-phosphate rise by about 25%. Other metabolites remain unchanged. After glucagon treatment, cytosolic pyruvate is decreased by 37%, whereas glutamate and 2-oxoglutarate decrease by 70%. The [NAD+]/[NADH] ratios calculated from the cytosolic concentrations of the reactants of lactate dehydrogenase and malate dehydrogenase were the same. Glucagon shifts this ratio and also that of the [NADP+]/[NADPH] couple towards a more reduced state. 4. In the mitochondrial space glucagon causes an increase in the acetyl-CoA and ATP contents by 25%, and an increase in [phosphoenolpyruvate] by 50%. Other metabolites are not changed by glucagon. Oxaloacetate in the matrix is only slightly decreased after glucagon, yet glutamate and 2-oxoglutarate fall to about 25% of the respective control values. The [NAD+]/[NADH] ratios as calculated from the [3-hydroxybutyrate]/[acetoacetate] ratio and from the matrix [malate]/[oxaloacetate] couple are lowered by glucagon, yet in the latter case the values are about tenfold higher than in the former. 5. Glucagon and oleate stimulate gluconeogenesis from lactate to nearly the same extent. Oleate, however, does not produce the changes in cellular 2-oxoglutarate and glutamate as observed with glucagon. 6. The changes of the subcellular metabolite distribution after glucagon are compatible with the proposal that the stimulation of gluconeogenesis results from as yet unknown action(s) of the hormone at the mitochondrial level in concert with its established effects on proteolysis and lipolysis.
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August 1977
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Research Article|
August 15 1977
Effect of glucagon on metabolite compartmentation in isolated rat liver cells during gluconeogenesis from lactate
Elmar A. Siess;
Elmar A. Siess
1Forschergruppe Diabetes und Klinisch-Chemisches Institut, Städtisches Krankenhaus München-Schwabing, 8000 München 40, Kölner Platz 1, Federal Republic of Germany
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Dietrich G. Brocks;
Dietrich G. Brocks
1Forschergruppe Diabetes und Klinisch-Chemisches Institut, Städtisches Krankenhaus München-Schwabing, 8000 München 40, Kölner Platz 1, Federal Republic of Germany
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Herbert K. Lattke;
Herbert K. Lattke
1Forschergruppe Diabetes und Klinisch-Chemisches Institut, Städtisches Krankenhaus München-Schwabing, 8000 München 40, Kölner Platz 1, Federal Republic of Germany
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Otto H. Wieland
Otto H. Wieland
1Forschergruppe Diabetes und Klinisch-Chemisches Institut, Städtisches Krankenhaus München-Schwabing, 8000 München 40, Kölner Platz 1, Federal Republic of Germany
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1977 London: The Biochemical Society
1977
Biochem J (1977) 166 (2): 225–235.
Citation
Elmar A. Siess, Dietrich G. Brocks, Herbert K. Lattke, Otto H. Wieland; Effect of glucagon on metabolite compartmentation in isolated rat liver cells during gluconeogenesis from lactate. Biochem J 15 August 1977; 166 (2): 225–235. doi: https://doi.org/10.1042/bj1660225
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