Ribeiro M O, Lebrun F L, Christoffolete M A, Branco M, Crescenzi A, Carvalho S D, Negrão N, Bianco A C
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, Brazil 05508-900.
Am J Physiol Endocrinol Metab. 2000 Aug;279(2):E314-22. doi: 10.1152/ajpendo.2000.279.2.E314.
To study the thermal response of interscapular brown fat (IBF) to norepinephrine (NE), urethan-anesthetized rats (1.2 g/kg ip) maintained at 28-30 degrees C received a constant venous infusion of NE (0-2 x 10(4) pmol/min) over a period of 60 min. IBF temperatures (T(IBF)) were recorded with a small thermistor fixed under the IBF pad. Data were plotted against time and expressed as maximal variation (Deltat degrees C). Saline-injected rats showed a decrease in T(IBF) of approximately 0.6 degrees C. NE infusion increased T(IBF) by a maximum of approximately 3.0 degrees C at a dose of 10(4) pmol x min(-1) x 100 g body wt(-1). Surgically thyroidectomized (Tx) rats kept on 0.05% methimazole showed a flat response to NE. Treatment with thyroxine (T(4), 0.8 microg x 100 g(-1) x day(-1)) for 2-15 days normalized mitochondrial UCP1 (Western blotting) and IBF thermal response to NE, whereas iopanoic acid (5 mg x 100 g body wt(-1) x day(-1)) blocked the effects of T(4). Treatment with 3,5, 3'-triiodothyronine (T(3), 0.6 microg x 100 g body wt(-1) x day(-1)) for up to 15 days did not normalize UCP1 levels. However, these animals showed a normal IBF thermal response to NE. Cold exposure for 5 days or feeding a cafeteria diet for 20 days increased UCP1 levels by approximately 3.5-fold. Nevertheless, the IBF thermal response was only greater than that of controls when maximal doses of NE (2 x 10(4) pmol/min and higher) were used.
为研究肩胛间棕色脂肪（IBF）对去甲肾上腺素（NE）的热反应，将维持在28 - 30摄氏度的乌拉坦麻醉大鼠（腹腔注射1.2 g/kg）在60分钟内持续静脉输注NE（0 - 2×10⁴ pmol/分钟）。用固定在IBF垫下的小型热敏电阻记录IBF温度（T(IBF)）。数据以时间作图，并表示为最大变化量（Δt摄氏度）。注射生理盐水的大鼠T(IBF)下降约0.6摄氏度。在剂量为10⁴ pmol×分钟⁻¹×100 g体重⁻¹时，输注NE使T(IBF)最多升高约3.0摄氏度。接受0.05%甲巯咪唑的手术切除甲状腺（Tx）大鼠对NE反应平淡。用甲状腺素（T₄，0.8 μg×100 g⁻¹×天⁻¹）治疗2 - 15天可使线粒体解偶联蛋白1（UCP1，蛋白质免疫印迹法）和IBF对NE的热反应恢复正常，而碘番酸（5 mg×100 g体重⁻¹×天⁻¹）可阻断T₄的作用。用三碘甲状腺原氨酸（T₃，0.6 μg×100 g体重⁻¹×天⁻¹）治疗长达15天未使UCP1水平恢复正常。然而，这些动物对NE的IBF热反应正常。冷暴露5天或喂食自助餐饮食20天使UCP1水平升高约3.5倍。尽管如此，仅在使用最大剂量的NE（2×10⁴ pmol/分钟及更高）时，IBF热反应才大于对照组。
1）甲状腺功能减退与IBF对NE的热反应迟钝有关；2）线粒体UCP1浓度两到四倍的变化在输注NE期间不一定转化为产热。
