Catecholamines and triiodothyronine variations and the calorigenic response to norepinephrine in cold-adapted and exercise-trained rats.

Abstract

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.

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@article{Leblanc1982CatecholaminesAT, title={Catecholamines and triiodothyronine variations and the calorigenic response to norepinephrine in cold-adapted and exercise-trained rats.}, author={James F Leblanc and Audrey Labrie and D Lupien and Denis Richard}, journal={Canadian journal of physiology and pharmacology}, year={1982}, volume={60 6}, pages={783-7} }