The Influence of Thyroxine Treatment and Thyroidectomy on the Calorigenic and Some Other Metabolic Effects of Adrenaline and Noradrenaline in Experiments on Fasted Rabbits

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Abstract
In fasting rabbits studies were made of the influence of thyroidhormone on the calorigenic effect of adrenaline (A) and noradrenaline (NA) and their elevating actions on the concentration of lactic acid, glucose and free fatty acids (FFA) in the blood. Thyroxine treatment potentiated significantly the calorigenic and hyperlactacidemic effects of A in a dose of 0.5 μg/kg/min, but not that of 0.05 μg/kg/min. The hyperglycemic effect of A was weaker after thyroxine treatment, while its effect on the plasma FFA was not changed with certainty. After thyroidectomy the calorigenic and hyperlactacidemic effects of A were significantly diminished. In untreated animals the calorigenic, hyperlactacidemic and hypergly‐cemic effects of NA in a dose of 0.5 μg/kg/min were weaker than those of A in the same dose, while the effect on the plasma FFA was more marked. Thyroxine treatment did not with certainty influence any of the metabolic effects of NA. Most of the calorigenic effect of A could be ascribed to an increased lactic acid metabolism both in untreated, thyroidectomized and thyroxine treated rabbits. The influence of thyroid hormones on the calorigenic effect of A in rabbits may therefore be ascribed, at least in part, to an increased lactic acid production and metabolism.