Hind-leg heat losses in cold-exposed rats

Adán, C.; Ardévol, Anna; Closa, Daniel; Remesar, Xavier; Alemany, M.

doi:10.1016/0306-4565(94)00068-t

Cited by 4 publications

(6 citation statements)

References 18 publications

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“…However, the components of heat transfer to the environment vary considerably; the main source of heat is the transfer from blood to -mainly -muscle and skin, except during exercise, when most heat comes from the metabolic processes associated with muscular activity. This is a similar condition to that found in cold-exposure [2].…”

Section: Discussionsupporting

confidence: 84%

“…In spite of the heavy exercise performed, core and muscle temperature were maintained fairly well, a situation that contrasts with the changes observed under the apparently milder conditions of cold exposure [2]. Obese rats kept a tighter control than the lean rats on muscle and core temperature during exercise, helped by their larger mass, with lower temperature increases despite higher heat production.…”

Section: Discussionmentioning

confidence: 89%

“…Under resting conditions, muscle maintenance energy consumption accounts for only a fraction of total energy expenditure [2], but this situation changes during exercise, when the muscle energy output increases manyfold. The activity of the respiratory and circulatory systems increases in order to supply enough oxygen to the muscle [38].…”

Section: Introductionmentioning

confidence: 99%

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Hind leg heat balance in obese Zucker rats during exercise

Ardévol

Adán

Remesar

et al. 1998

Pfl�gers Archiv European Journal of Physiology

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To analyse the effect of obesity on exercise-derived heat dissipation, lean and obese Zucker rats were exercised on an inclined treadmill until they would no longer run with gentle prodding. We measured their oxygen consumption, water vapour loss, the concentrations of adenosine tri- and diphosphate, creatine phosphate, and lactate in quick-frozen leg muscles, and the temperature of muscle, skin and blood in the aorta. We determined blood flow to leg muscle, fat and skin by measuring the entrapment of fluorescent microspheres. From the measurements we calculated heat flow rates between hind leg muscle, blood, fat and skin and the environment. The obese rats weighed twice as much as the lean (340-400 g and 175-200 g respectively) and ran half as fast (113 +/- 7 m versus 257 +/- 17 m). The differences between the two groups for basal oxygen consumption (lean: 6.7 +/- 0.9 micromol/min, obese: 5.0 +/- 1.9 micromol/min) and exercising oxygen consumption (lean: 37.8 +/- 5.6 micromol/min, obese: 22.2 +/- 3.8 micromol/min) were not significant. Both groups stopped running after the same time at their maximal speed (lean: 4.5 +/- 0.3 min, obese: 4.2 +/- 0.2 min). During exercise, lean rats had higher increases in core temperature (lean: 0.7 degrees C, obese: 0.4 degrees C) and muscle temperatures (lean: 1.3 degrees C, obese: 0.7 degrees C) than the obese rats. The calculated heat flows indicated a predominant conductive transfer of heat from muscle through the skin in lean rats but a higher proportion of heat transfer to the blood in obese rats. It is concluded that muscle heat accumulation did not cause fatigue in either case.

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 89%

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Hind leg heat balance in obese Zucker rats during exercise

Ardévol

Adán

Remesar

et al. 1998

Pfl�gers Archiv European Journal of Physiology

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“…Our data show that hindquarters oxygen consumption increased considerably during coldinduced shivering thermogenesis, as previously demonstrated in young oxen (Bell, Thomson & Findlay, 1974), non-cold-acclimated ducklings (Duchamp & Barre, 1993) and rats (Adan, Ardevol, Closa, Remesar, Alemany & Fernandez-Lopez, 1995). This rise was explained by an increase in both aortic blood flow and oxygen extraction by the hindquarters.…”

Section: Cardiovascular Adaptationssupporting

confidence: 89%

“…Indeed, capillary to fibre ratio has been shown to increase with age in parallel with the percentage of red fibres in rats (Sillau & Banchero, 1977), and the enhancement of muscle blood flow during shivering is higher in slow-oxidative than in fastglycolytic fibres in rabbits (Zoccoli, Cianci, Lenzi & Franzini, 1992) and piglets (G. Lossec Besides, cold-induced changes in blood flow were also associated with a marked enhancement of oxygen extraction at both ages. These concurrent and extremely rapid (15-30 min) mechanisms have also been reported in young oxen (Bell et al 1974) and rats (Adan et al 1995), and are probably necessary to support the acute enhancement of the energy needs of the shivering muscle during short-term cold exposure. On the contrary, during cold acclimation, the rise in skeletal muscle oxygen consumption resulted mainly from the increase in muscle blood flow with no changes in oxygen extraction in ducklings (Duchamp & Barre, 1993).…”

Section: Cardiovascular Adaptationsmentioning

confidence: 53%

Age‐related changes in oxygen and nutrient uptake by hindquarters in newborn pigs during cold‐induced shivering

Lossec¹,

Lebreton²,

Hulin³

et al. 1998

Experimental Physiology

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SUMMARYNewborn pigs rely essentially on shivering thermogenesis in the cold. In order to understand the rapid postnatal enhancement of thermogenic capacities in piglets, the oxygen and nutrient uptake of hindquarters was measured in vivo in 1-(n = 6) and 5-day-old (n = 6) animals at thermal neutrality and during cold exposure. The hindquarters were considered to represent a skeletal muscle compartment. Indirect calorimetry and arterio-venous techniques were used. The cold challenge (23°C at 1 day old and 15°C at 5 days old for 90 min) induced a similar increase (+90 %) in regulatory heat production at both ages. Hindquarters blood flow was higher at 5 days than 1 day old at thermal neutrality (26 + 3 vs. 17 + 1 ml min-' (100 g hindquarters)-') and its increase in the cold was much more marked (+65 % at 5 days old vs. +25 % at 1 day old). Oxygen extraction by the hindquarters rose from 30-35 % at thermal neutrality to 65-70 % in the cold at both ages. The calculated contribution of skeletal muscle to total oxygen consumption averaged 34-40% at thermal neutrality and 50-64% in the cold and skeletal muscle was the major contributor to regulatory thermogenesis. Based on hindquarters glucose uptake and lactate release, carbohydrate appeared to be an important fuel for shivering. However, net uptake of fatty acids increased progressively during cold exposure at 5 days old. The enhancement in muscular blood supply and fatty acid utilization during shivering is probably related to the postnatal improvement in the thermoregulatory response of the piglet.

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