Force development and metabolism in skeletal muscle of euthyroid and hypothyroid rats.

The effects of thyroid hormone depletion on skeletal muscle metabolism in relation to force development were studied. For this purpose, the triceps surae muscles were perfused and stimulated at 5 Hz. The basal oxygen consumption of the skeletal muscle preparation was 50% lower in hypothyroid rats as compared with euthyroid rats. The results show that: 1. Active force development was the same in euthyroid and hypothyroid rats during 30 min of stimulation. 2. The increase in oxygen consumption during contraction was twice as high in the euthyroid group compared with the hypothyroid group. 3. Lactate release and glucose consumption were considerably high in the euthyroid group than in the hypothyroid group during the last 15 min of stimulation. The data show that force development is not impaired in hypothyroid rats but, on the contrary, indicate that the contraction process proceeds more economically in hypothyroid rats than in euthyroid rats.