Thioredoxin and glutaredoxin systems of rat liver cytosol are not influenced by thyroid dysfunction.

The relation of thyroid hormone status to the function of hepatic cytosolic components activating microsomal reverse triiodothyronine (rT3) 5'-monodeiodination was studied in rats. Hyperthyroidism was induced by administration of thyroxine and hypothyroidism, by thyroidectomy. The DTT-stimulated microsomal rT3 5'-monodeiodination rate was increased by 125% in hyperthyroid rats and reduced to about 30% in hypothyroid rats (when compared with euthyroid animals). Thyroid status was unrelated to NADPH-dependent activation of microsomal 5'-deiodinase by cytosol components or to cytosolic concentrations of thioredoxin and glutaredoxin, which stimulate in vitro microsomal deiodination of thyroid hormone.