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

Male Wistar rats, aged 6 weeks, were maintained at 25 degreesC for 9 to 11 weeks (W group), at 10 degreesC for 9 to 11 weeks (C group), and at 25 degreesC for 2 weeks after exposure to 10 degreesC for 9 weeks (D group). Thermogenesis at 10 degreesC was significantly greater than at 25 degreesC. Thermogenesis per body mass in the C group was greater than in the W and D groups. The RQ value at 10 degreesC was greater than at 25 degreesC 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 acclimation for 9 weeks, is lost because of a decreased secretion of calorigenic hormones, in spite of a slight decrease in BAT mass, during deacclimation for 2 weeks.