DIRECT EFFECTS OF 3,5,3'-TRIIODOTHYRONINE AND 3,5-DIIODOTHYRONINE ON MITOCHONDRIAL METABOLISM IN THE GOLDFISH CARASSIUS-AURATUS

Direct effects of 3,5,3'-triiodothyronine (T-3) and 3,5-diiodothyronin e (T-2) on the metabolism of the goldfish (Carassius auratus) were ass essed using mitochondria isolated from liver and red muscle. Following a 5-min incubation with either T-3 or T-2, the oxidation rates of sub strates involved in amino acid and carbohydrate metabolism and lipid c atabolism were measured. State 3 oxidation of pyruvate was significant ly higher for liver mitochondria treated with T-2 and for red muscle m itochondria incubated with T-3 when compared to control mitochondria. Rapid elevation of state 3 rates of substrate oxidation by thyroid hor mones may be important in mediating diurnal changes in mitochondrial m etabolism. Significant increases in liver and red muscle mitochondrial state 4 rates were also observed for pyruvate in T-2- and T-3-treated mitochondria and for glutamate in T-3-treated mitochondria. (C) 1996 Academic Press, Inc.