title: Control of norepinephrine turnover in brown adipose tissue of Syrian hamsters.
abstract: Sympathetic nervous system activity in brown adipose tissue (BAT) of normal and myopathic Syrian hamsters was assessed by measuring norepinephrine turnover rate (NETR) using [3H]norepinephrine. Acute exposure of normal hamsters to cold (4 degrees C) for 4 or 24 h increased norepinephrine secretion but not resynthesis. By 3 days and at 2 wk in the cold, NETR increased but returned to a normal level by 6 wk. Hamsters were initially hypothermic (to 3 days) then normothermic (2 and 6 wk). Adaptation of normal or myopathic hamsters to high-fat diet or short photoperiod (4 h light, 20 h dark) for up to 12 wk did not alter NETR in BAT. Serum triiodothyronine (T3) concentration increased rapidly in the cold to reach a maximum level by 24 h at which it remained for 6 wk and was not correlated with changes in NETR in BAT. The high-fat diet did not alter T3 level in normal hamsters; it increased the low T3 level in myopathic hamsters. Short photoperiod induced a transient increase in T3 level in normal hamsters but not in myopathic hamsters. We conclude that the hypertrophied state of BAT in Syrian hamsters adapted to cold, to high-fat diet, or to short photoperiod is not maintained by elevated norepinephrine secretion and that some other factor(s) must be involved. A selective increase in concentration of BAT mitochondrial uncoupling protein in hamsters may be dependent on raised T3 level in serum and/or production in BAT, since both occur in response to cold acclimation but not in response to high-fat diet or short photoperiod.
authors: Department of Biochemistry, University of Ottawa, Ontario, Canada.
authors: S L
authors: SL
authors: Sigurdson
authors: J
authors: J
authors: Himms-Hagen
mesh_terms: D000064:Acclimatization; D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000818:Animals; D003080:Cold Temperature; D006224:Cricetinae; D003624:Darkness; D004041:Dietary Fats; D006706:Homeostasis; D008027:Light; D008297:Male; D008647:Mesocricetus; D009137:Muscular Dystrophy, Animal / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D012016:Reference Values
chemical_list: D004041:Dietary Fats; D009638:Norepinephrine