Cold acclimation of hypothyroid rats

Sellers, EA; Flattery, K. V.; Steiner, G.

doi:10.1152/ajplegacy.1974.226.2.290

Cited by 30 publications

(16 citation statements)

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“…In fact, our hypothyroid cold-exposed rats showed neither the increase in the percentage contribution made by BAT to total body weight seen in hypothyroid T3-treated cold-exposed animals nor an increased oxidative potential (as a consequence of increased UCP synthesis). This is also in agreement with previous studies showing that for T3 at a dose of 5 µg/100 g BW, adrenergic input was required to increase UCP messenger ribonucleic acid (mRNA) levels significantly [27]. However, even though it has already been reported that T3 is critical for the full response of BAT to cold, it is not clear whether endogenous T3 produced from T4 or exogenously administered T3 is more effective [4,24].…”

Section: Role Of T3 In Cold Induced Thermogenesissupporting

confidence: 90%

“…It is well known that hypothyroid rats die after a short period of cold exposure, and that they survive if they receive the thyroid hormones 3,3′,5-triiodo-L-thyronine (T3) or thyroxine, (T4) [27,29]. The recruitment of brown adipose tissue (BAT) by cellular processes such as proliferation, differentiation and uncoupling protein (UCP) synthesis followed by its incorporation into the mitochondria, is thought to be one of the most important physiological adaptive responses to cold stress.…”

Section: Introductionmentioning

confidence: 99%

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3,5-Diiodo- l -thyronine and 3,5,3′-triiodo- l -thyronine both improve the cold tolerance of hypothyroid rats, but possibly via different mechanisms

Lanni

Moreno

Lombardi

et al. 1998

Pfl�gers Archiv European Journal of Physiology

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The effects of 3,5-diiodo-L-thyronine (3,5-T2, 2.5-10 microg/100 g BW) on cold tolerance, energy expenditure and oxidative capacity of four metabolically very active tissues (brown adipose tissue, skeletal muscle, liver and heart) were determined in hypothyroid, cold-exposed rats. Hypothyroid rats survived cold for only 3-4 days. 3,5-T2 improved survival dose dependently; with 10 microg/100 g BW the rats survived 3 weeks (limit of observation). This effect was paralleled by an increased energy expenditure of the whole animal for the entire 3 weeks. Similar effects were observed in hypothyroid rats treated with 3,3',5-triiodo-L-thyronine (T3). 3,5-T2 stimulated the specific oxidative capacity (expressed as cytochrome oxidase activity per milligram protein) of all four tissues dose dependently. When the oxidative capacity was expressed as total activity (cytochrome oxidase activity times organ weight), the percentage increases were of the same order. T3 exerted similar effects, but the changes in total activity were much greater than in specific activity, indicating an effect on the tissue trophism. The effect of 3,5-T2 on cold tolerance thus mimics the effect of T3, but via different cellular mechanisms. T3 seems to act primarily on the trophism of the tissues, while 3,5-T2 may act directly on mitochondria without an effect on tissue trophism.

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Section: Role Of T3 In Cold Induced Thermogenesissupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

3,5-Diiodo- l -thyronine and 3,5,3′-triiodo- l -thyronine both improve the cold tolerance of hypothyroid rats, but possibly via different mechanisms

Lanni

Moreno

Lombardi

et al. 1998

Pfl�gers Archiv European Journal of Physiology

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“…On the other hand, enhanced sympathetic activity is not sufficient, in and of itself, to cause BAT hypertrophy because exposure to hypoxia (0.5 atmosphere) for 14 d increased IBAT sympathetic activity, but not tissue mass (32), and food restriction during cold exposure limited IBAT growth, but not sympathetic activation (33). Thyroid hormone, which can induce BAT hypertrophy in rats when administered in hyperthyroid doses (24), may not be an important growth factor for BAT in the situations studied here because IBAT hypertrophies in hypothyroid animals exposed to cold (34,35) or fed the "cafeteria" These studies, therefore, demonstrate that sympathetic outflow to IBAT in the rat changes markedly in situations known to affect thermogenesis. The findings are consistent with an important role for the sympathetic nervous system in the regulation of heat production by BAT and the overall control of thermogenesis in this animal.…”

mentioning

confidence: 98%

Effect of Diet and Cold Exposure on Norepinephrine Turnover in Brown Adipose Tissue of the Rat

Young¹,

Saville²,

Rothwell³

et al. 1982

J. Clin. Invest.

336

153

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A B S T R A C T Brown adipose tissue (BAT)is an important site of adaptive changes in thermogenesis in the rat. The sympathetic nervous system, which richly supplies BAT, is thought to play an important role in the regulation of BAT thermogenesis because catecholamines stimulate and beta adrenergic blocking agents inhibit oxygen consumption in this tissue. The present studies were carried out to assess directly sympathetic activity in BAT in response to cold exposure and to changes in dietary intake, both of which alter heat production in the rat. Sympathetic activity was determined from the rate of norepinephrine (NE) turnover in interscapular brown adipose tissue (IBAT) after preliminary experiments validated the use of NE turnover techniques in IBAT. Acute exposure to 4°C increased NE turnover in IBAT 4-to 12-fold compared with ambient temperature controls, depending upon the interval over which the turnover measurement was made, while in the heart NE turnover doubled in response to the same cold stimulus. In animals exposed to cold continuously for 10 d before study, NE turnover measurements in IBAT and in the heart were elevated comparably to those obtained during acute exposure. Alterations in feeding were also associated with changes in NE turnover in IBAT. Fasting for 2 d decreased NE turnover in IBAT (-35% from 29.2±4.2 ng NE/h to 18.9±5.9) and in heart (-52%). In animals fed a "cafeteria" diet, a model of voluntary overfeeding in the rat, NE turnover was increased in both IBAT (+108% from 24.8±4.5 ng NE/h to 51.7±6.8) and heart (+66%). Because ganglionic blockade exerted a greater effect on NE turnover in IBAT in cafeteriafed rats than in controls, the increase in NE turnover in IBAT with this overfeeding regimen reflects enhanced central sympathetic outflow. Thus NE turnover techniques can be satisfactorily applied to the

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“…BAT mass. N A secretion and thermo genic capacity are reduced [8]. Thyroid hor mone is needed for an efficient NST [8.…”

Section: Discussionmentioning

confidence: 99%

The Thermoregulation of the Nude Mouse

Weihe¹

1984

Pathobiology

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Cold acclimation of hypothyroid rats

Cited by 30 publications

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3,5-Diiodo- l -thyronine and 3,5,3′-triiodo- l -thyronine both improve the cold tolerance of hypothyroid rats, but possibly via different mechanisms

3,5-Diiodo- l -thyronine and 3,5,3′-triiodo- l -thyronine both improve the cold tolerance of hypothyroid rats, but possibly via different mechanisms

Effect of Diet and Cold Exposure on Norepinephrine Turnover in Brown Adipose Tissue of the Rat

The Thermoregulation of the Nude Mouse

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