Carnitine and acetylcarnitine in skeletal and cardiac muscle.

The acetylcarnitine/carnitine ratio has been found significantly increased in tibial muscles of swimming rats in comparison with normal rats. Analogous increase occurred in electrically stimulated tibial muscle in comparison with the unstimulated controlateral muscle of the same animal. Swimming also induced a statistically significant increase of the acetylcarnitine/carnitine ratio in heart, while norepinephrine administration resulted in a decrease of carnitine not accompanied by a corresponding increase in acetylcarnitine in a severe carnitine depletion of cardiac muscle. These results are discussed in terms of carnitine function in the acetyl metabolism, assuming the acetylcarnitine as a possible acetyl reservoir in the working muscle.