1. The effects of hypothyroidism on the sensitivity of glycolysis and glycogen synthesis to insulin were investigated in the isolated, incubated soleus muscle of the rat. 2. Hypothyroidism, which was induced by administration of propylthiouracil to the rats, decreased fasting plasma levels of free fatty acids and increased plasma levels of glucose but did not significantly change plasma levels of insulin. 3. The sensitivity of the rates of glycogen synthesis to insulin was increased at physiological, but decreased at supraphysiological, concentrations of insulin. 4. The rates of glycolysis in the hypothyroid muscles were decreased at all insulin concentrations studied and the EC50 for insulin was increased more than 8-fold; the latter indicates decreased sensitivity of this process to insulin. However, at physiological concentrations of insulin, the rates of glucose phosphorylation in the soleus muscles of hypothyroid rats were not different from controls. This suggests that hypothyroidism affects glucose metabolism in muscle not by affecting glucose transport but by decreasing the rate of glucose 6-phosphate conversion to lactate and increasing the rate of conversion of glucose 6-phosphate to glycogen. 5. The rates of glucose oxidation were decreased in the hypothyroid muscles at all insulin concentrations.
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Research Article|
January 15 1989
Effects of hypothyroidism on the sensitivity of glycolysis and glycogen synthesis to insulin in the soleus muscle of the rat
G D Dimitriadis;
G D Dimitriadis
1Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
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B Leighton;
B Leighton
1Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
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M Parry-Billings;
M Parry-Billings
1Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
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D West;
D West
1Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
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E A Newsholme
E A Newsholme
1Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1989 London: The Biochemical Society
1989
Biochem J (1989) 257 (2): 369–373.
Citation
G D Dimitriadis, B Leighton, M Parry-Billings, D West, E A Newsholme; Effects of hypothyroidism on the sensitivity of glycolysis and glycogen synthesis to insulin in the soleus muscle of the rat. Biochem J 15 January 1989; 257 (2): 369–373. doi: https://doi.org/10.1042/bj2570369
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