Adaptive changes in the thermogenesis of rats by cold acclimation and deacclimation

Male Wistar rats, aged 6 weeks, were maintained at 25 degrees C for 9 to 11 weeks (W group), at 10 degrees C for 9 to 11 weeks (C group), and at 25 de grees C for 2 weeks after exposure to 10 degrees C for 9 weeks (D group). T hermogenesis at 10 degrees C was significantly greater than at 25 degrees C . Thermogenesis per body mass in the C group was greater than in the W and D groups. The RQ value at 10 degrees C was greater than at 25 degrees C in the W group, whereas the opposite was observed in the C and D groups. It is suggested that a large part of enhanced thermogenesis, caused by cold accl imation for 9 weeks, is lost because of a decreased secretion of calorigeni c hormones, in spite of a slight decrease in BAT mass, during deacclimation for 2 weeks.