Catecholamines and triiodothyronine variations and the calorigenic response to norepinephrine in cold-adapted and exercise-trained rats.
A comparison was made of the thermogenic response to norepinephrine (NE) in cold-adapted (2 h per day at -15 degrees C for 5 weeks) and in exercise-trained rats (2 h swimming per day for 5 weeks). The oxygen consumption and the plasma catecholamine elevation were comparable for both conditions. Similarly plasma corticosterone determinations indicated comparable elevations in acute stress exposure and reduced responses in both exercise-trained and cold-adapted rats. The marked increase in colonic temperature which was observed in cold-adapted animals injected with NE (30 micrograms/100 g s.c.) was not found in exercise-trained rats. Similarly the brown adipose tissue was double in size in the cold-adapted rats but remained unchanged with exercise training. An important elevation of triiodothyronine (T3) was found in cold-exposed rats, either adapted or not. However, exercise was found to decrease plasma T3 in trained and nontrained rats. The results indicate that swimming for 2 h and exposure to cold (-15 degrees C) for 2 h produced comparable elevation of plasma corticosterone and catecholamine, and of oxygen consumption. However, only the cold-adapted animals develop a NE-induced thermogenesis. It is suggested that thyroid hormones are necessary as permissive factor, in stress-induced thermogenesis.
D000064:Acclimatization; D002001:Adipose Tissue, Brown / Q000378:metabolism; D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D002395:Catecholamines / Q000097:blood*; D003080:Cold Temperature; D003345:Corticosterone / Q000097:blood; D005260:Female; D009638:Norepinephrine / Q000494:pharmacology*; D010101:Oxygen Consumption; D010805:Physical Conditioning, Animal; D051381:Rats; D011919:Rats, Inbred Strains; D014284:Triiodothyronine / Q000097:blood*
D002395:Catecholamines; D014284:Triiodothyronine; D003345:Corticosterone; D009638:Norepinephrine