1983 Volume 29 Issue 4 Pages 413-428
This study was undertaken to investigate the changes incarnitine metabolism in rats and mice injected with T4 for 3 days and 10 days, respectively, and in rats fed a T3 and T4-supplemented diet for 6 weeks. Thyroid hormone administration brought about a significant in crease in urinary excretion of total carnitine. In T3 +T4-treated ratsurinary esterified-carnitine to free-carnitine ratio increased significantly inthe later phase of administration. Carnitine pool size in the body was sig nificantly decreased in both T4-injected mice and T3 +T4-fed rats. In thelatter animals, this decrease was due to the reduced carnitine contents inorgans other than the liver, especially in skeletal muscle. The amount ofcarnitine synthesized by control and T3 + T4-treated rats was calculatedfrom the data on carnitine intake, urinary carnitine excretion and carni tine pool size in the body over the 6-week period. Values obtained were 66.2±3.2 (mean±SEM) μmol/rat and 28.5±4.9 μmol/rat, respectively, and the difference was significant (p<0.05). These results indicate thatcarnitine synthesis is depressed by thyroid hormone, however, some pos sibilities that thyroid hormone may increase carnitine synthesis were alsodiscussed.
