Changes in glucose metabolism and cardiovascular responses in thyroidectomized streptozotocin treated diabetic rats

Abstract

Two weeks after streptozotocin i.v. injection, changes in glucose metabolism, levels of serum and urinary calcium, magnesium and copper, and cardiovascular responses were investigated in thyroidectomized streptozotocin treated diabetic rats. These parameters were compared to those of intact rats. Serum and urinary calcium, magnesium and copper concentrations were not influenced by thyroidectomy. Glycosylated hemoglobin (HbA₁) in thyroidectomized streptozotocin treated diabetic rats was higher than that in those which were thyroidectomized alone. In thyroidectomized rats that induction of hyperglycemia required a larger dose of streptozotocin than for intact rats. Norepinephrine (0.3125, 0.625, 1.25 μg/kg i.v.)-induced pressor response and ACh (0.3125, 0.625, 1.25, 2.5 μg/kg i.v.)-induced depressor responses were both reduced in streptozotocin treated diabetic rats. These reduced pressor and depressor responses tended to recover after thyroidectomy. These results suggest that hypothyroid states may partially improve glucose metabolism and cardiovascular responses in streptozotocin treated diabetic rats.