Cs. Hotz et al., DIETARY IODINE AND SELENIUM INTERACT TO AFFECT THYROID-HORMONE METABOLISM OF RATS, The Journal of nutrition, 127(6), 1997, pp. 1214-1218
The interaction of dietary selenium and iodine on the activities of th
e selenoenzymes, selenium-dependent glutathione peroxidase (GSH-Px), a
nd type I deiodinase (DI-I), and the thyroid hormones thyroxine (T4) a
nd triiodothyronine (T3) were studied. Male weanling Sprague-Dawley ra
ts were fed an AIN-93G diet for 6 wk with modified selenium and iodine
concentration as follows: three levels each of iodine and selenium (0
.03, 0.2 added and 1.0 added mg iodine/kg diet, and 0.05, 0.18 added a
nd 1.0 added mg selenium/kg diet) were used in a 3 x 3 factorial desig
n. Renal, but not hepatic, DI-I activity was lower in rats with low se
lenium intake than in controls. Circulating T3 concentration was not a
ffected by the dietary levels of iodine or selenium. Unlike in liver,
kidney and erythrocytes, thyroidal GSH-Px activity was not lower than
in controls in rats with low selenium intake, but was significantly hi
gher when iodine intake was low. Significant interactions of iodine an
d selenium on serum T4 and thyroidal GSH-Px activity were observed. Se
rum T4 was maintained at control levels when both dietary iodine and s
elenium were low, but not when iodine alone, or selenium alone, was lo
w, Activity of thyroidal GSH-Px was lowest in rats fed a diet containi
ng high iodine and low selenium. The results suggest that high iodine
intake, when selenium is deficient, may permit thyroid tissue damage a
s a result of low thyroidal GSH-Px activity during thyroid stimulation
. A moderately low selenium intake normalized circulating T4 concentra
tion in the presence of iodine deficiency.