[Effect of thyroxine and noradrenaline on the energetics of muscle contraction].

The highly sensitive thermometric method (1.10(-5) degrees C/mm) revealed that the heat production of single contraction of the isolated rat diaphragmal muscle with artificial hyperthyrosis (HD) is nearly double of that of the normal muscle (ND). Noradrenaline added to the inculation solution entailed a greater increase of heat production of the muscle contraction in HD and had no significant effect on ND. However, calorific effect of thyroid hormone was about twice and a half as great as that of noradrenaline. These data suggest that thyroxin acts independently in the energy regulation during the cold acclimation of the organism, and the calorific effects of both hormones can be more effectively realized just at the moment of muscle contraction.