Studies on the mechanism of action of thyroid stimulating hormone on glucose oxidation

Abstract

Incubation of thyroid slices with added thyroid stimulating hormone results in an increase in the concentration of oxidized triphosphopyridine nucleotide. Since thyroid stimulating hormone also stimulates acetate and pyruvate oxidation, it is suggested that the previously reported increase in glucose oxidation is not a primary effect of thyroid stimulating hormone but results secondarily from the ability of this hormone to increase the TPN concentration in the thyroid. Attempts to demonstrate an effect of thyroid stimulating hormone on TPNH oxidase were unsuccessful, and it was not possible to stimulate glucose oxidation in thyroid homogenates fortified with TPN or TPNH. The amount of glucose oxidized by thyroid homogenates appeared to be a function of the concentration of TPN added. An effect of 3·4·1 o −11 M TSH was obtained when dog thyroid slices were used. This concentration is considered to be in the physiological range. Monoiodotyrosine and diiodotyrosine also stimulated glucose oxidation in thyroid slices. Acetylated thyroid stimulating hormone neither stimulated glucose oxidation in thyroid slices nor did it inhibit the action of one-tenth as much thyroid stimulating hormone. Thyroid glands obtained from guinea pigs injected with thyroid stimulating hormone for two days prior to sacrifice oxidized more glucose than did glands from control animals.