title: Placental 5-deiodinase activity and fetal thyroid hormone economy are unaffected by selenium deficiency in the rat.
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 placental 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.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, University of Massachusetts Medical Center, Worcester 01655.
authors.forename: J P
authors.initials: JP
authors.lastname: Chanoine
authors.forename: S
authors.initials: S
authors.lastname: Alex
authors.forename: S
authors.initials: S
authors.lastname: Stone
authors.forename: S L
authors.initials: SL
authors.lastname: Fang
authors.forename: I
authors.initials: I
authors.lastname: Veronikis
authors.forename: J L
authors.initials: JL
authors.lastname: Leonard
authors.forename: L E
authors.initials: LE
authors.lastname: Braverman
mesh_terms: D000818:Animals; D001921:Brain / Q000196:embryology / Q000201:enzymology; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D007453:Iodide Peroxidase / Q000032:analysis*; D008297:Male; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000378:metabolism*; D011257:Pregnancy Proteins / Q000032:analysis*; D051381:Rats; D012643:Selenium / Q000008:administration & dosage / Q000172:deficiency* / Q000502:physiology; D013961:Thyroid Gland / Q000196:embryology* / Q000378:metabolism; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*
chemical_list: D011257:Pregnancy Proteins; D014284:Triiodothyronine; D013972:Thyrotropin; D007453:Iodide Peroxidase; D012643:Selenium; D013974:Thyroxine