Effects of thyroidectomy and thyroxine supplement on the glucose metabolism in the rat anterior pituitary.

Abstract

The isolated anterior pituitary of the rat produced a greater amount of 14CO2 from glucose-1-14C than from glucose-6-14C. Thyroidectomy resulted in a significant increase in the 14CO2 production from glucose-1-14C by the anterior pituitary, and the increased 14CO2 output was suppressed to the normal level 72 hr. after L-thyroxine (T4) administration in vivo. Oxidation of glucose-U-14C and glucose-6-14C was also increased slightly after thyroidectomy, but the C1/C6 ratio of 14CO2 was greater in the thyroidectomized group than in the normal control. These data show that the hexose monophosphate pathway in the anterior pituitary is markedly stimulated after thyroidectomy and seem to indicate that 14C-glucose oxidation via glycolysis is also accelerated to a lesser extent. Incorporation of 14C-glucose carbon into glycogen, RNA and protein was accelerated after thyroidectomy and returned to the normal levels 72 hr. after T4 supplement. The absolute amount of glucose consumed by the anterior pituitary increased after thyroidectomy and returned to normal 72 hr. after T4 supplement. In contrast, the formation of radioactive lipids from 14C-glucose was reduced by thyroidectomy and returned to normal 72 hr. after T4 supplement. The correlation of the glucose metabolism in the anterior pituitary with the protein and RNA synthesis was discussed, with special reference to the functional state of the thyroid gland.