Noradrenaline turnover in brown adipose tissue and the heart of fed and fasted golden hamsters

The effect of fasting on sympathetic activity in tissues of the golden hamster has been investigated using measurements of noradrenaline turnover. Fasting for 60 h did not have a significant effect on noradrenaline turnover, both fractional and total, in brown adipose tissue or the heart. Fasting did, however, result in a functional atrophy of brown adipose tissue; tissue weight, protein content, and cytochrome oxidase activity were each reduced after a 60-h fast. These results suggest that the atrophy of brown adipose tissue induced by fasting in the golden hamster does not relate to a major decrease in sympathetic activity. The findings add further support for the view that the thermogenic capacity of brown adipose tissue is not primarily dependent on sympathetic activity in the golden hamster.     

冷暴露对中缅树鼩适应性产热特征的影响

在冷暴露(5 ± 1℃)1 d,7 d,14 d 和21d 对中缅树鼩的肝脏、心脏、膈肌、腓肠肌和褐色脂肪组织(BAT)的总蛋白和线粒体蛋白含量、线粒体的状态Ⅳ呼吸能力、细胞色素C 氧化酶活力及血清中甲状腺激素的水平等指标进行了测定。结果表明:冷暴露过程中肝脏线粒体蛋白含量对低温的反应比总蛋白的反应剧烈,心脏和BAT 组织的线粒体蛋白含量也随着冷驯化时间的延长而显著增加,但腓肠肌的反应较为温和;各组织线粒体的状态Ⅳ呼吸能力均显著增强,除腓肠肌外其它各组织细胞色素C 氧化酶活性也随冷暴露时间的延长而急剧增加。说明在低温条件下,肝脏、腓肠肌、心脏和BAT 等组织都参与了体温调节的过程,在自然生境中,低温是重要的刺激产热的调节因子。     

The effects of temperature acclimation on organ/tissue mass and cytochrome c oxidase activity in juvenile cod (Gadus morhua)

Cod were acclimated to 5 and 15° C (cold and warm acclimation, respectively) for at least 43 days after which tissue-somatic indices, tissue protein, DNA content, and cytochrome c oxidase (CCO) activity were measured. Liver, stomach, intestine, total heart and ventricle-somatic indices were all increased significantly in the cold acclimated animals compared with their warm acclimated counterparts. There were no differences in gill or white muscle-somatic indices between the acclimation temperatures. Tissue protein concentration (mg protein g tissue⁻¹) was generally unaffected by temperature acclimation. Cold acclimation resulted in higher white muscle and lower ventricle CCO specific activities(μmol cytochrome c oxidized min⁻¹· g tissue⁻¹) compared with the respective warm acclimated tissues. No significant differences in CCO specific activity were observed in the remaining tissues (when measured at an intermediate temperature of 10° C). Total tissue CCO activity (measured at an intermediate temperature of 10° C) did not differ significantly between the cold and warm acclimated fish.     

Assessment of brown adipose tissue activity in rats by 99mTc-sestamibi uptake

Brown adipose tissue (BAT) physiology and imaging have recently attracted considerable attention. BAT is characterized both by enhanced perfusion and increased mitochondrial activity. (99m)Tc-sestamibi is a lipophilic cationic tracer that concentrates in mitochondria. Data on the accumulation of (99m)Tc-sestamibi in BAT are currently lacking. This study investigates the in vivo (99m)Tc-sestamibi uptake in rat BAT. (99m)Tc-sestamibi was administered in male Wistar rats of various age and body size. (99m)Tc-sestamibi uptake was measured in vitro in BAT and white fat (WF) together with cytochrome c oxidase activity. Both (99m)Tc-sestamibi uptake and cytochrome c oxidase activity were higher in BAT than in WF (P<0.05). (99m)Tc-Sestamibi uptake in both BAT and WF was negatively related to body weight (r = -0.96 and -0.89, respectively) as was the BAT/WF uptake ratio (r = -0.85). These data show a higher (99m)Tc-sestamibi uptake in BAT compared to WF, in agreement with the high mitochondrial content and respiratory activity of the former. The strong negative correlation between (99m)Tc-sestamibi uptake in BAT and body weight (negative allometry), is in accordance to increased needs of thermogenesis in smaller animals. Implications of increased (99m)Tc-sestamibi uptake in BAT in radionuclide imaging are also discussed.     

Adaptive changes in the concentration of the mitochondrial ‘uncoupling’ protein in brown adipose tissue of hamsters acclimated at different temperatures

The effect of acclimation at different temperatures on the activity of interscapular brown adipose tissue has been investigated in the hamster, a hibernator. Between 31° and 4°C the cytochrome oxidase activity of the tissue increased 4- to 5-fold, mitochondrial GDP binding per mg of mitochondrial protein doubled, and the amount of uncoupling protein rose from 1.7% to 5.4% of total mitochondrial protein. It is concluded that there are clear adaptive changes induced by temperature in brown adipose tissue of the hamster, but the changes are limited in comparison with those in the mouse.     

Measurement of brown adipose tissue uncoupling protein by enzyme linked immunosorbent assay

Antibody to uncoupling protein (UCP) purified from rat brown adipose tissue (BAT) was raised in rabbits and an enzyme linked immunosorbent assay was developed. The antiserum did not cross-react with other mitochondrial proteins from BAT and from other tissues but cross-reacted with UCP from hamster, guinea pig and mouse. The assay is capable of detecting 5 ng of UCP. Using this assay and a crude mitochondrial preparation, UCP content of BAT was shown to increase during cold adaptation.     

Postnatal appearance of uncoupling protein and formation of thermogenic mitochondria in hamster brown adipose tissue

Brown adipose tissue of developing hamster was characterized by western blotting, enzyme activity measurements and immunoelectron microscopy. During the first postnatal week the tissue contained significant amounts of differentiating mitochondria and comparable quantities of active cytochrome oxidase and ATP synthase. The uncoupling protein appeared on the 7/8th day and its specific content increased 80-times between day 8 and day 17. In parallel, the specific content and activity of cytochrome oxidase increased 3-times but ATP synthase decreased 2-times. The total content of uncoupling protein and of cytochrome oxidase in interscapular brown adipose tissue increased 360- and 11-times, respectively. Analysis of isolated mitochondria showed that the observed differences result mainly from changes of the enzymic equipment of the mitochondrial membrane. During the same interval, propylthiouracil-insensitive "type II' thyroxine 5'-deiodinase activity in brown adipose tissue increased 10-times. It was concluded that the thermogenic function of the hamster brown adipose tissue develops after the first postnatal week due to highly differentiated synthesis of mitochondrial proteins leading to replacement of preexisting, uncoupling protein-lacking nonthermogenic mitochondria by thermogenic ones, similarly as shown in brown adipose tissue of the embryonic mouse and rat (Houst?k, J., et al. (1988) Biochim. Biophys. Acta 935, 19-25).     

Effect of the beta(3)-adrenergic agonist Cl316,243 on functional differentiation of white and brown adipocytes in primary cell culture

We investigated the effect of the specific beta(3)-adrenergic receptor agonist CL 316,243 (CL) on proliferation and functional differentiation of the Siberian hamster (Phodopus sungorus) white and brown preadipocytes in primary cell culture. Proliferation of both white and brown preadipocytes was stimulated by a general beta-adrenergic agonist (isoproterenol) but not by CL. Lipolysis of differentiated white and brown adipocytes was stimulated similarly by CL with maximum effect at 10 nM. Thermogenic properties of cells were assessed by immunodetection of UCP-1, the brown adipocyte specific uncoupling protein, and measurement of cytochrome c oxidase (COx) activity as an index of mitochondrial capacity. UCP-1 content was largely increased by CL in BAT but not in WAT cultures. Basal UCP-2 mRNA levels were similar in WAT and BAT cultures and increased by both CL and isoproterenol. COx activity of BAT cultures was twice as high as that of WAT cultures but in neither cell culture system could it be increased by beta-adrenergic stimulation. We suggest (i) that white and brown preadipocyte proliferation is increased in vitro via beta1 or beta(2), but not beta(3)-adrenergic pathways, (ii) that white and brown preadipocytes represent different cell types, and (iii) that in vitro beta-adrenergic stimulation it is not sufficient to induce complete thermogenic adaptation of brown adipocytes.     

达乌尔黄鼠产热的季节性变化

达乌尔黄鼠（Ｃｉｔｅｌｌｕｓｄａｕｒｉｃｕｓ）的产热表现出明显的季节性变化。在非冬眠期,静止代谢率（ＲＭＲ）和非颤抖性产热（ＮＳＴ）于春季最高,秋季次之,夏季最低。冬眠期,ＲＭＲ降到极低水平,只为春季的３．０％。肝脏的线粒体蛋白含量、线粒体呼吸和细胞色素Ｃ氧化酶活力在秋季显著高于其它各季。褐色脂肪组织（ＢＡＴ）的重量、线粒体蛋白含量、细胞色素Ｃ氧化酶活力和α－磷酸甘油氧化酶活力,在夏季处于一年中的最低水平,到了冬季这些指标达到一年中的最高水平。在非冬眠季节ＢＡＴ产热能力升高时,ＮＳＴ能力也相应升高,这表明ＢＡＴ产热能力的增强是ＮＳＴ能力提高的部分机制。达乌尔黄鼠血清Ｔ＿４含量在年周期中没有明显改变,冬眠时血清Ｔ＿３含量显著高于其它各季。     

Seasonal adaptation of brown adipose tissue in the Djungarian hamster

Summary The composition and oxidative capacity of brown adipose tissue (BAT) were investigated in Djungarian hamsters kept under natural photoperiod, either indoors at neutralT _a (23°C) or under outdoor conditions. BAT comprises up to 5% of the body weight in summer/indoor hamster, with lipid representing 86% of the total tissue mass. Tissue mass and thermogenic capacity are inversely related during seasonal adaptation: 30% decrease of total DNA, accompanied by extensive lipid depletion, reduces the amount of BAT by almost 60% during acclimatization from summer/indoor to winter/outdoor conditions. Mitochondrial protein in BAT is increased by a factor of 2.6 concomitantly, and by a factor of 4 when related to body weight (body weight reduction 36%).Cytochrome oxidase activity in different brown fat deposits varies by up to 150% in summer/indoor hamsters; depending on the fat pad, the enzyme activity is increased 200%–700% during adaptation to winter/outdoor conditions.Natural photoperiod is decisive in determining the seasonal adaptation of DNA content in BAT and of body weight. Short photoperiod alone may lead to depletion of lipid content of BAT and thus decrease the tissue mass practically to the lowest seasonal level, even though both parameters may be also influenced byT _a. One third of the maximum adaptive increase of tissue mitochondria may be attributed to seasonal changes in photoperiod and up to two thirds toT _a. Photoperiod establishes a fixed fundament of slow-reacting functional adaptation of BAT, whereas the effect of decreasedT _a depends on the rate and duration of cold influence.Abbreviations BAT brown adipose tissue - NST nonshivering thermogenesis - T _a ambient temperature     

Ontogeny of cardiac rate regulation and brown fat thermogenesis in golden hamsters (Mesocricetus auratus)

It was shown previously in infant rats (Rattus norvegicus) that the ability to produce heat in the cold using brown adipose tissue (BAT) is closely related to the ability to maintain cardiac rate. When the limits of BAT thermogenesis were exceeded, interscapular temperature (which reflects the temperature of the interscapular BAT depot) and cardiac rate fell together. As an extension of this earlier study, the relation between BAT thermogenesis and cardiac rate was examined here in the golden hamster (Mesocricetus auratus), a species whose young do not exhibit BAT thermogenesis until the end of the 2nd week postpartum. It was found that 3 to 12-day-old hamsters were unable to increase shivering or nonshivering thermogenesis in the cold and exhibited decreases in cardiac rate that proceeded in lock-step with decreases in interscapular temperature. In contrast, as the thermogenic capability of hamsters increased after 12 days of age, cardiac rate was maintained within narrow limits across a wide range of air temperatures. These results support the hypothesis that heat produced by BAT helps to warm the heart and thus aids in the maintenance of cardiac rate during cold exposure. Accepted: 16 August 1997     

光照和温度对根田鼠褐色脂肪组织产热能力的影响

测定了根田鼠在室内驯化2周后褐色脂肪组织（BAT）的蛋白含量、线粒体蛋白含量和细胞色素C氧化酶活性的变化。动物进行如下4种处理:23℃,16L:8D;23℃,8L：16D;5℃,16L：8D和5℃,8L:16D.。结果表明,短光照可刺激根田鼠的BAT线粒体细胞色素C氧化酶的活性增加;低温驯化可导致根田鼠的BAT线粒体蛋白含量增加;短光照加低温可进一步促进酶的活性增加。结合个体水平的产热特点,说明根田鼠在产热能力的季节驯化过程中,光周期是一主要的季节调节信号,环境温度进一步增强光照的作用,环境温度和光周期共同作用以诱导其产热能力等方面的生理调节。研究结果支持了环境温度和光周期共同作用以调节动物产热变化的学说。     

Brown fat temperature decrease by electrical stimulation of in and around retrorubral field in the golden hamster

Electrical stimulation (0.1 ms, 1 mA, 5–50 Hz) of the ventral midbrain of the golden hamster decreased frequency-dependent temperatures of the interscapular brown adipose tissue (IBAT) and rectum. The loci where electrical stimulation evoked continuous decrease in IBAT temperature during the stimulation for 5 min were localized in and around the retrorubral field. Results suggest that tonic inhibitory mechanism on BAT thermogenesis exists in the homologous region of the hamster brain to the rat brain in the previous study.     

Responses to cafeteria feeding in mice after the removal of interscapular brown adipose tissue

Feeding acafeteria diet to mice resulted in an increased energy intake of approximately 30% and this led to increases in the wet weight, total protein content , and total cytochrome oxidase activity of interscapular and dorso-cervical brown adipose tissue. Surgical removal of interscapular brown adipose tissue, followed by cafeteria feeding, gave rise to an elevation in dorso-cervical brown adipose tissue wet weight, total protein content, and total cytochrome oxidase activity, compared to intact cafeteria-fed mice. Cafeteria feeding with or without the removal of interscapular brown adipose tissue did not lead to significant increases in body weight compared to stock-fed control mice, but both cafeteria-fed groups of mice showed significant elevations in body fat content indicating that the induced hyperphagia led to a relative obesity in the cafeteria-fed groups. The results presented are consistent with an increased thermogenic activity in the brown adipose tissue of cafeteria-fed mice, and the effect of the removal of interscapular brown adipose tissue further indicates the quantitative importance of the tissue in the control of body weight.     

The development of the Chondrocranium in the golden hamster, Mesocricetus auratus (Waterhouse).

3 -stages of development of the chondrocranium of the golden hamster have been described. The chondrocrania of the gerbil, mouse and white rat have been compared with the chondrocranium of the golden hamster and the main differences noted. In several respects, the chondrocranium of the golden hamster is primitive.     

Effects of phenobarbitone on hepatic microsomal enzyme activity and liver blood flow in spontaneously hypertensive rats.

Hepatic microsomal enzyme activity, liver blood flow and pentobarbitone sleeping time were determined in spontaneously hypertensive rats (SHR) and normotensive Wistar rats (NR) after pretreatment with saline or phenobarbitone. In NR and SHR the increases in total liver blood flow produced by phenobarbitone were sufficient to maintain liver perfusion despite the increase in liver weight and in both strains of rat the increase was entirely due to increased portal venous return. Saline pretreated SHR had shorter pentobarbitone sleeping times than control NR and their livers had greater total cytochrome c reductase activities and total microsomal protein than those of NR but cytochrome P-450 contents were not significantly different. Phenobarbitone significantly shortened sleeping times in both strains but NR still slept longer than SHR. Total microsomal protein, cytochrome P-450 content and cytochrome c reductase activity were increased by phenobarbitone in both SHR and NR but the increases in cytochrome P-450 and cytochrome c reductase were greater in the hypertensive rats.     

Lipoprotein lipase in adipose tissues of rats running during cold exposure

This study evaluated the individual and combined effects of exercise training and intermittent cold exposure of similar energy cost on serum lipids and lipoprotein lipase (LPL) activity on epididymal white (WAT) and interscapular brown (BAT) adipose tissues of the rat. The animals were subjected daily to 2 h of treadmill running at 24 degrees C or for the same period of time at -5 degrees C, with or without exercise, for 28 days. Exercise training lowered serum triglycerides (P less than 0.01), whereas serum cholesterol was reduced by cold exposure (P less than 0.05). Cholesterol lowering occurred in the lipoproteins of lower densities. WAT weight was diminished by both treatments. Exercise training had an overall lowering effect on WAT total LPL activity (P less than 0.05), whereas cold exposure did not affect enzyme activity significantly. Exercise and intermittent cold interacted on BAT weight. Cold increased total BAT LPL activity (P less than 0.03), whereas simultaneous exercise in the cold greatly diminished this effect. Serum insulin levels were not affected by either treatment. Thus, in WAT, intermittent exposure to cold did not have any lasting effect on LPL activity, whereas exercise training decreased the latter. In contrast, exercise did not influence LPL in BAT of rats not exposed to cold but prevented the stimulation of enzyme activity induced by repeated cold exposure. These results support the notion that the regulation of LPL is tissue specific.     

Gender-related differences in morphology and thermogenic capacity of brown adipose tissue mitochondrial subpopulations

To investigate the possible existence of a gender dimorphism in the morphology and functionality of brown adipose tissue (BAT) mitochondrial subpopulations, we obtained three mitochondrial fractions - heavy, medium and light - by differential centrifugation. Electron microscopic analysis was carried out and mitochondrial protein content, cytochrome c oxidase and ATP synthase activities, mitochondrial DNA content and UCP1 protein levels were measured in each mitochondrial fraction. Female rats showed a greater mitochondrial size than males, with a different distribution pattern of the subpopulations. These differences were accompanied by higher oxidative and thermogenic capacities and a higher protein content in female rat BAT. This tissue also showed a greater tendency to respiratory chain uncoupling, as well as a close coordination between the oxidative, phosphorylative and thermogenic processes. These differences were found in the heavy subpopulation but not in the light one. Our results demonstrate that female rat BAT shows a highly differentiated mitochondrial pool, with the heavy mitochondrial subpopulation as the main responsible for the greater thermogenic activity of this tissue. In addition, it seems that there is a differential regulation of the mitochondrial growth cycle between genders in BAT, which leads to enhanced thermogenic capacity in female rat mitochondria.     

长爪沙鼠褐色脂肪组织和肝脏产热特征的季节性变化

长爪沙鼠（Meriones unguiculatus）是一种栖息于典型草原和荒漠草原非冬眠群居性的小型哺乳动物。为研究其产热功能的季节变化,我们分别在2003年秋季（9月下旬）、冬季（11月下旬）、2004年春季（3月底-4月下旬）和夏季（7月下旬）,分别测定了其体重、褐色脂肪组织和肝脏的重量、线粒体总蛋白含量和细胞色素c氧化酶活力,以及褐色脂肪组织中解偶联蛋白1（Uncoupling protein1,UCPl）的含量等。结果显示：除雄鼠的体重显著高于雌鼠外,其它各项指标均无性别差异。体重和褐色脂肪组织的重量都在冬季较高,显著高于夏季,而肝脏的重量在夏季显著高于其它季节。褐色脂肪组织和肝脏的线粒体蛋白含量和细胞色素c氧化酶活力以及UCP1含量,都在冬季较高,夏季较低。这些结果表明：在野外条件下,褐色脂肪组织和肝脏在细胞水平上产热能力的提高和UCP1含量的增加,是长爪沙鼠抵御寒冷的重要方式。