Abstract
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^3^HOH from [2‐^3^H]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‐^14^C]glucose and D‐[6‐^14^C]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 a 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.