title: Thyroxine 5'-deiodination in brown adipose tissue and pineal gland: implications for thermogenic regulation and role of melatonin.
abstract: T4 type II 5'-deiodinase (5'-D II) activity was studied in wild-captured Richardson's ground squirrels. As previously reported for other species, 5'-D II activity was detected in frontal cortex, cerebellum, pineal gland, and brown adipose tissue (BAT); in the median eminence the levels of 5'-D II activity were undetectable with our methodology. When pineal gland, frontal cortex, and cerebellum nyctohemeral profiles were studied, none of them showed variations. Cold exposure for 4 h led to an increase in the enzymatic activity 10-fold above the basal values for BAT, while in the pineal gland the values were doubled; cold exposure failed to change the 5'-D II activity in the frontal cortex. Acute melatonin treatment caused a 7-fold increase in 5'-D II activity in BAT, but did not affect enzyme activity in either the pineal gland or frontal cortex. The data indicate that 5'-D II in Richardson's ground squirrel shows classical localizations. Additionally, two new regulatory factors of 5'-D II are reported, i.e. melatonin for BAT and cold for the pineal gland.
authors.affiliation: Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284.
authors.forename: M
authors.initials: M
authors.lastname: Puig-Domingo
authors.forename: J M
authors.initials: JM
authors.lastname: Guerrero
authors.forename: R J
authors.initials: RJ
authors.lastname: Reiter
authors.forename: M J
authors.initials: MJ
authors.lastname: Tannenbaum
authors.forename: E C
authors.initials: EC
authors.lastname: Hurlbut
authors.forename: A
authors.initials: A
authors.lastname: Gonzalez-Brito
authors.forename: C
authors.initials: C
authors.lastname: Santana
mesh_terms: D002001:Adipose Tissue, Brown / Q000187:drug effects / Q000201:enzymology*; D000818:Animals; D001833:Body Temperature Regulation; D002531:Cerebellum / Q000187:drug effects / Q000201:enzymology; D002540:Cerebral Cortex / Q000187:drug effects / Q000201:enzymology; D003080:Cold Temperature; D005260:Female; D007453:Iodide Peroxidase / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008297:Male; D008473:Median Eminence / Q000187:drug effects / Q000201:enzymology; D008550:Melatonin / Q000502:physiology*; D008713:Methimazole / Q000494:pharmacology; D010870:Pineal Gland / Q000201:enzymology*; D012589:Sciuridae / Q000378:metabolism*; D013974:Thyroxine / Q000378:metabolism
chemical_list: D007457:Iodine Radioisotopes; D008713:Methimazole; D007453:Iodide Peroxidase; D008550:Melatonin; D013974:Thyroxine