Morphological and enzymehistochemical changes in the interscapular adipose tissue of adult guinea-pigs during prolonged exposure to cold

Chronic alcohol intake induces the oxidative capacity of brown adipose tissue in the rat

The present study was carried out to elucidate the effect of long-term alcohol intake on the oxidative capacity of brown adipose tissue in the rat. Rats housed at room temperature were given water containing 10% ethanol for six months, while controls received water alone. Fully cold-acclimated rats (exposed to +4 degrees C for 6 weeks) served as the second control group. Alcohol did not alter the food intake of the rats compared with the controls kept at room temperature, but it did cause a mean decrease of 8 ml in fluid consumption. There was no difference in the increase in body weight between the groups housed at room temperature. Body weight of the rats exposed to cold did not change during cold acclimation. No morphological liver changes were observed in alcohol-fed rats, but some changes related to long-term alcohol consumption were found in the myocardium. Chronic alcohol intake increased the quantity of brown adipose tissue and its protein content but changes were not as great as in the cold-acclimated rats nor did alcohol increase protein content per unit of the adipose tissue as did cold. On the other hand, the specific activity of mitochondrial cytochrome oxidase increased by 90% and that of succinate dehydrogenase by 130% in alcohol-fed rats, whereas specific activities of these enzymes displayed little or no change in the cold-acclimated rats. Results suggest that chronic alcohol ingestion induces the oxidative capacity of the interscapular brown adipose tissue in the rat, increasing the mass of BAT and specific activities of mitochondrial enzymes.

Age-related changes in thermoregulation in male albino rats

Male Sprague Dawley rats were followed longitudinally from 3 to 24 months of age. Resting oxygen consumption (VO2), measured in the thermal neutral zone (29 +/- 1.0 degrees C) decreased 47% between 3 and 24 months of age with a stable period from 6 to 9 months. Changes in rectal temperature in general followed changes in VO2. On the average the decline in rectal temperature from 3 to 24 months was 0.8 degrees C. Thermal conductance dropped initially from 3 to 6 months and remained stable during further age periods. Thermal circulation index rose slightly from 3 to 13 months, and dropped thereafter from 13 to 24 months. When animals were exposed to a mild cold challenge (18-19 degrees C for 90 min.), the increase in VO2 was the same from 3 to 13 months of age. At 24 months this increase was significantly higher. The capacity for non-shivering thermogenesis (NST) measured after norepinephrine stimulation declined from 3 to 6 months, remained stable from 6 to 9 months and declined to 13 months. The capacity for NST after a mild cold challenge was significantly decreased at 24 months of age. These results suggest that shivering thermogenesis (ST) may be the main source of heat production in the old organism when faced with a mild cold challenge. Since ST is more energy consuming than NST it may explain the accidental hypothermia which occurs often in the elderly.

The occurrence of brown adipose tissue in outdoor workers

Histochemical reactions and activities of mitochondrial enzymes in adipose tissue around the neck arteries and in pericardium were studied in men who had been outdoor workers in northern Finland. The purpose was to study the occurrence of brown fat in workers having been exposed to cool or cold ambient temperature. Indoor workers of the same age were used as controls. Histochemically, no mitochondrial enzyme reactions were seen in the adipose tissues taken from the indoor workers, whereas some outdoor workers had some multilocular adipose tissue, mostly around the neck arteries. Biochemical parameters also showed increased enzyme activities of aerobic energy metabolism in the adipose tissue of these people. The present results suggest that working in the cold can retain brown adipose tissue in "strategic" places in human adults.

Temperature acclimation in the Mongolian gerbil (Meriones unguiculatus): biochemical and organ weight changes

1. Adult Mongolian gerbils (Meriones unguiculatus) were acclimated to 5 +/- 1, 24 +/- 1 and 34 +/- 1 degrees C for 6-8 weeks. 2. Body weights of temperature acclimated gerbils did not differ significantly from controls. Organ wt/body wt ratios of liver, kidney and heart increased in cold-acclimated and decreased in heat-acclimated gerbils. Adrenal wt/body wt ratio increased in the cold and was unchanged in the heat. Relative weights of brain, spleen, lungs, brown fat and ovaries + uterus did not change with temperature acclimation. 3. Cold acclimation produced significant increases in specific and total activity of brown fat alpha GPO and liver SO and AAO and in total activity of kidney SO; a significant decrease in liver mitochondrial ADP/O ratio with succinate as substrate; and no change in brown fat SO or liver alpha KGO. 4. Heat acclimation produced significant decreases in specific and total activity of liver and kidney SO, and in total activity of brown fat SO and alpha GPO, and liver AAO and alpha KGO. 5. The combined biochemical and organ wt changes seen in temperature-acclimated gerbils suggest that this species is capable of altering its metabolic thermogenic potential in response to a wide range of ambient temperatures.

Serum glucose, serum free fatty acids and adipose tissue lipids after fatal hypothermia of cold acclimatized, reserpine or propranolol treated guinea-pigs

Surviving ability in frost (-20 degree C) was studied in cold acclimatized guinea-pigs given either reserpine, propranolol or saline. Survival time, rectal temperature at death, serum glucose, serum FFA and triglycerides in the interscapular adipose tissue were determined. Rectal temperature was highest in the reserpine group, in the same animals that endured the frost the shortest time. The survival time had decreased by about a half of that in the controls. Propranolol treatment decreased the living time only slightly. The fact that serum glucose remained high in the reserpine treated animals was obviously related to the short survival time. In the propranolol group glucose values were somewhat higher than in the control group (saline-animals). Reserpine seemed to have inhibited the release of FFA in the warm-acclimatized animals as interpreted from the low serum values. On the other hand, FFA were rather high in the cold-acclimatized reserpine animals. The blocking effect of reserpine reflected also in the higher contents of triglycerides in the adipose tissue both in cold-acclimatized and warm-acclimatized animals. Propranolol prevented slightly the depletion of the triglycerides. Amount of total lipids in the adipose tissue was lower in the cold-acclimatized animals than in the warm-acclimatized ones because of the change of the type of the adipocytes from unilocular to multilocular. The results corroborated the importance of FFA for longer survival in severe cold. Sensitization to reserpine seems to develop during cold-acclimatization. It calls attention to a possible hazard of reserpine treatment in cold environment.