title: Acute cold exposure, leptin, and somatostatin analog (octreotide) modulate thyroid 5'-deiodinase activity.
abstract: We investigated the effect of acute cold exposure, leptin, and the somatostatin analog octreotide (OCT) on thyroid type I (D1) and II (D2) deiodinase activities. Microsomal D1 and D2 activities were measured by the release of (125)I from (125)I-reverse triiodothyronine (rT(3)) under different assay conditions. Rats exposed to 4 degrees C (15, 30, 60, and 120 min) showed progressive reduction in thyroidal D1 and D2, reaching approximately 40% at 2 h (P < 0.05) despite increased circulating TSH (P < 0,05) associated with the higher thyroid D1 and D2 in hypothyroid rats. A single injection of leptin (8 microg/100 g body wt sc) induced increased thyroid and liver D1 (P < 0.05), but not thyroid D2, activities at 30 and 120 min, independently of the serum TSH rise shown only at 2 h. OCT (1 microg/kg body wt sc) increased D1 and D2 activity significantly 24 h after a single injection, with no changes in serum TSH. Therefore, leptin and somatostatin are potential physiological upregulators of thyroid deiodinases, and their low secretion during acute cold exposure may be a potential mechanism contributing to cold-induced reduction in thyroid deiodinase activity.
authors.affiliation: Laboratório de Endocrinologia Molecular, Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21949-900 Rio de Janeiro, Brazil.
authors.forename: Patricia Cristina
authors.initials: PC
authors.lastname: Lisboa
authors.forename: Karen Jesus
authors.initials: KJ
authors.lastname: Oliveira
authors.forename: Adriana
authors.initials: A
authors.lastname: Cabanelas
authors.forename: Tania Maria
authors.initials: TM
authors.lastname: Ortiga-Carvalho
authors.forename: Carmen Cabanelas
authors.initials: CC
authors.lastname: Pazos-Moura
mesh_terms: D000818:Animals; D003080:Cold Temperature; D006728:Hormones / Q000494:pharmacology*; D007037:Hypothyroidism / Q000139:chemically induced / Q000378:metabolism; D007453:Iodide Peroxidase / Q000378:metabolism*; D020738:Leptin / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D015282:Octreotide / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D006728:Hormones; D020738:Leptin; D014284:Triiodothyronine; D013972:Thyrotropin; D007453:Iodide Peroxidase; D013974:Thyroxine; D015282:Octreotide