Short-Term Influence of 3,5,3'-Triiodothyronine Infusion on Resting Metabolic Rate of the Young Pig

Summary

The influence of 3,5,3'-triiodothyronine (T₃) on resting metabolic rate (RMR) has been examined in the young pig. A dose of 10, 20 or 40 nmol T₃/kg body weight was infused intravenously for periods of between one and 4 h and oxygen consumption and activity were measured over the following 20 h. There was no change in RMR during the period of T₃ infusion. Results 12-20 h after infusion were influenced neither by the time at which the animal was fed nor by the length of infusion. Immediately after infusion there was a marked increase in plasma T₃ concentration, followed by a rapid decline. Levels were much higher than those recorded previously after feeding. Only after 40 nmol T₃/kg was there a significant 12% increase in RMR during the period 12-20 h after infusion (P < 0.02). The significance of these results in relation to the source of the postprandial increase in plasma T₃ and the action of thyroid hormones at the cellular level is discussed.

Key words

Thyroid Hormones - Resting Metabolic Rate - Pig - Diet-Induced Thermogenesis