STIMULATION OF CARNITINE ACYLCARNITINE TRANSLOCASE ACTIVITY IN HEART-MITOCHONDRIA FROM HYPERTHYROID RATS

The effect of hyperthyroidism on fatty acid oxidation and on carnitine -acylcarnitine translocase activity in rat heart mitochondria has been studied, The rates of palmitoylcarnitine supported respiration as wel l as the carnitine-palmitoylcarnitine exchange reaction were both stim ulated (approx, 36%) in heart mitochondria from hyperthyroid rats, Kin etic analysis of the carnitine-carnitine exchange reaction showed that thyroid hormone affects the V-max of this process, while having no ef fect on the K-m values. The level of cardiolipin was significantly hig her (approx, 40%) in heart mitoplasts from hyperthyroid rats than from the control rats. It can be concluded that thyroid hormones produce a stimulation of heart mitochondrial carnitine translocase activity and that the basis of this effect is likely an increase in the cardiolipi n content.