Changes of peripheral tissue thyroid hormone metabolism in rats fed with selenium- and vitamin E-deficient artificial semisynthetic diet.

OBJECTIVE

To examine the relationship between selenium (Se)- and vitamin E(VE)-deficiency and thyroid hormone (TH) metabolic disturbance, especially type I iodothyronine 5'-deiodinase (ID-I) activity.

METHODS

We observed the metabolic changes of TH-3, 3',5-triidothyronine (T3) and thyroxin (T4) and their free radicals-glutathione peroxidase (GSH-Px) and lipid peroxides (LPO) in the peripheral tissues (liver, kidney and blood) of Wistar rats maintained on Se- and VE-deficient artificial semi-synthetic diet for 8 weeks.

RESULTS

In the Se- and VE-deficient rats (compared with Se- and VE-supplement rats): 1). Hepatic and renal ID-I activities decreased by 60% and 50% respectively, serum levels of T3 reduced 36%, and T4 increased by 32%. Hepatic ID-I activity and serum T3 concentration in Se- and VE-supplement rats were significantly higher than those in the Se-supplement and VE-deficient rats. 2). GSH-Px activities in the whole blood and liver decreased by 61% and 82% respectively. LPO concentrations in serum and liver increased by 53% and 40% respectively. When Se content remained the same, changes of VE content did not significantly affect GSH-Px activity, but the combined supplement of Se and VE decreased significantly the LPO concentration.

CONCLUSIONS

The data suggests that GSH-Px activity is influenced mainly by Se level, but ID-I activity is influenced by VE concentration in addition to Se level. VE seemed to play a protective role on ID-I and its mechanism might be related to the fact that VE protects the stability of microsomal membrane in which ID-I exists, avoiding from free radical damage as well as the coordinated action and mutual sparing effect of Se and VE.