Changes in glutathione status and 3,5,3'-triiodothyronine action in livers of rats given cysteine-deficient diets

Abstract

1. For a period of 32 d young rats were given a diet containing (g/kg) 220 casein, 120 casein +1.93 L-cysteine (Cys), or 120 casein.2. The formation of 3,5,3'-triiodothyronine (T3)-nuclear protein complexes was reduced in rats fed on the Cys-deficient diet.3. Scatchard analysis showed that decreased formation of T3-nuclear protein complexes was due to a decreased affinity of T3receptors; this decrease was induced, at least in part, by a reduced glutathione content.4. In rats fed on the Cys-deficient diet there was an expected decrease in growth but an unexpected increase in the activities of glucose-6-phosphate dehydrogenase (EC1.1.1.49) and malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) (EC1.1.1.40). It is suggested that this increase is related to an increased oxidized glutathione: reduced glutathione ratio.