Abstract
ABSTRACT: In adult male rats, selenium deficiency results in a near complete loss in the selenoprotein 5'-deiodinase in the liver, resulting in decreased peripheral deiodination of thyroxine (T4) and increased serum T4 concentrations. Serum 3,5,3'-triiodothyronine concentrations are normal or slightly decreased, and serum 3,3',5'-triiodothyronine concentrations are normal or slightly increased in selenium-deficient rats. We now report the effects of selenium deficiency on maternal and fetal thyroid hormone economy and on placenta! 5-deiodinase activity in the rat. Weanling female rats were fed either a selenium-deficient or selenium-supplemented diet for 4 wk before mating and then throughout gestation. Rats were killed at 21 d of gestation. Selenium deficiency was confirmed by a 95 and 94% decrease in glutathione peroxidase and a 84 and 56% decrease in liver type I outer ring 5' deiodinase activity in the mother and the fetus, respectively. In contrast to the increase in circulating T4 observed in selenium-deficient male and nonpregnant female adult rats, serum T4 was not affected by selenium deficiency in pregnant rats, but there was a 3-fold increase in serum 3,3',5'-triiodothyronine concentrations associated with a 70% decrease in maternal brain type II outer ring 5' deiodinase activity. Maternal serum 3,5,3'-triiodothyronine concentrations were decreased by 21%. Placental 5-deiodinase activity was unaffected by selenium deficiency. In the fetus, serum T4, 3,3',5'-triiodothyronine, and TSH concentrations were not affected by selenium deficiency. These data suggest that placental 5-deiodinase is not a selenoenzyme and that the failure of selenium deficiency to increase serum T4 concentrations in the mother as well as the minor role played by liver type I outer ring 5' deiodinase in the fetus results in the protection of fetal thyroid hormone economy against the potentially deleterious effects of selenium deficiency.
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Chanoine, JP., Alex, S., Stone, S. et al. Placental 5-Deiodinase Activity and Fetal Thyroid Hormone Economy Are Unaffected by Selenium Deficiency in the Rat. Pediatr Res 34, 288–292 (1993). https://doi.org/10.1203/00006450-199309000-00009
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DOI: https://doi.org/10.1203/00006450-199309000-00009
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