Enzymatic, metabolic and secretory perturbations in pancreatic islets of thyroidectomized rats.
In thyroidectomized rats, the activity of FAD-linked glycerophosphate dehydrogenase was severely diminished in liver homogenates but not affected significantly in pancreatic islet homogenates, whilst the activity of 2-ketoglutarate dehydrogenase was decreased modestly in both liver and islet homogenates. Likewise, in intact islets of thyroidectomized rats, the generation of 3HOH from [2-3H]glycerol was not decreased, and the ratio between oxidative and total glycolysis not significantly lower than in islets from sham-operated rats, at least in the presence of a high concentration of D-glucose. Nevertheless impaired oxidation of both D-[3,4-14C]glucose and D-[6-14C]glucose was observed in islets of thyroidectomized rats, the relative magnitude of such a decrease being more pronounced at a low than at a high D-glucose concentration. Such metabolic anomalies coincided with a lower level of plasma insulin and decreased output of insulin by islets incubated at low (2.8 mM), but not higher, concentrations of D-glucose. It is concluded that hypothyroidism does not mimic the deficiency in islet FAD-linked glycerophosphate dehydrogenase activity found in rats with inherited or acquired non-insulin-dependent diabetes.
Sener
A
A
Laboratory of Experimental Medicine, Erasmus Medical School, Brussels Free University, Belgium.
Malaisse-Lagae
F
F
Gervy-Decoster
C
C
Malaisse
W J
WJ
D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D002237:Carbohydrate Dehydrogenases / Q000032:analysis*; D005947:Glucose / Q000378:metabolism; D005969:Glutamate Dehydrogenase / Q000032:analysis; D005990:Glycerol / Q000378:metabolism; D007328:Insulin / Q000097:blood / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000201:enzymology*; D007655:Ketoglutarate Dehydrogenase Complex / Q000032:analysis; D008099:Liver / Q000201:enzymology; D013965:Thyroidectomy; D013974:Thyroxine / Q000097:blood
D001786:Blood Glucose; D007328:Insulin; D002237:Carbohydrate Dehydrogenases; C056470:3-glycerophosphate dehydrogenase; D007655:Ketoglutarate Dehydrogenase Complex; D005969:Glutamate Dehydrogenase; D005947:Glucose; D005990:Glycerol; D013974:Thyroxine