Metabolic adjustments during adaptation to high ambient temperature by preoptic-lesioned rats.
Metabolic adjustment was studied in male Wistar rats weighing 180-200 g with bilateral electrolytic lesions in the preoptic area which were acclimatized to a hot environment (34 degrees C, 30 rats) and to normal temperature (25 degrees C, 20 rats) for 60 days. Oxygen consumption at 34 degrees C and body weight were measured periodically. Preoptic-lesioned rats (PO rats) showed a reduction in metabolic rate (from 46.2 +/- 2 to 33 +/- 2 Cal/m2 per h, P less than 0.05) regardless of the temperatures to which they were adapted. Although the reduced metabolic rate of PO rats living at 25 degrees C or 34 degrees C could be an indicator of adaptation to heat, only the PO rats living at 25 degrees C showed a weight gain (101 +/- 13 g) similar to that observed for the sham-operated control (75 +/- 11 g). In fact, the PO rats living at 34 degrees C failed to increase their body weight during 60 days of exposure to heat. These data indicate that the preoptic area is essential to integrate the thermal input with the energy-linked metabolic process involved in adaptation to hot environments.
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GL
Departamento de Fisiologia, Universidade Federal do Pará, Belém, Brasil.
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D000222:Adaptation, Physiological; D000818:Animals; D001835:Body Weight; D004734:Energy Metabolism; D006358:Hot Temperature; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D011301:Preoptic Area / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains