The effect of fatty acid on the uptake of thyroxine by the perfused rat heart.

1. A study has been made of the effect of fatty acids on the uptake of thyroxine by the perfused rat heart.2. Oleic acid increases the thyroxine uptake of hearts perfused by solutions containing serum. In the absence of serum, oleic acid is without action.3. The thyroxine uptake of hearts perfused by 0.25% serum is approximately doubled by the addition of oleic acid at a concentration of 0.0025 m-equiv/l. An effect on thyroxine uptake, however, is demonstrable at only one twentieth of this concentration.4. Long-chain fatty acids are much more effective than short-chain fatty acids.