The Role of Adenosine 3′,5′-Phosphate in Mediating Effects of Thyroid-stimulating Hormone on Carbohydrate Metabolism of Bovine Thyroid Slices

Abstract

Abstract The possible role of adenosine 3',5'-phosphate in mediating certain effects of thyroid-stimulating hormone (TSH) on the carbohydrate metabolism of bovine thyroid slices has been studied by examination of the TSH concentration dependence of the effects, the effects of theophylline on the parameters, and the effects of N6,2'-O-dibutyryl adenosine 3',5'-phosphate. Evidence has been obtained that adenosine 3',5'-phosphate mediates TSH-induced depression of 14CO2 obtained from glucose-1-14C and TSH-stimulated accumulation of lactate in the medium. TSH, at concentrations that lowered the yield of 14CO2 from glucose-1-14C, did not influence the quantity of 14CO2 obtained from glucose-6-14C. The mechanism of this effect is unclear, but does not appear to involve enhancement of glycogenolysis. The oxidation of pyruvate-14C to 14CO2 has also been studied, and the evidence suggests that adenosine 3',5'-phosphate is not involved in the stimulation of this oxidation by TSH. Adenosine 3',5'-phosphate also does not appear to be a mediator of the TSH-stimulated oxidation of glucose-1-14C to 14CO2 which is apparent only at high concentrations of TSH in bovine thyroid slices. Changes in the total concentration of oxidized and reduced triphosphopyridine nucleotides were not apparent with levels of TSH that stimulated the oxidation of glucose-1-14C to 14CO2.