Short‐term control of mitochondrial adenine nucleotide translocator by thyroid hormone

Abstract

1. An improved simple technique for measuring adenine nucleotide translocator activity at low medium substrate concentrations is described. 2. Confirming previous reports, thyroidectomy was shown to lead to lowered translocator activity in rat liver mitochondria. The rapidly exchangeable portion of the matrix nucleotide also decreased in hypothyroid preparations even though the total nucleotides increased substantially. 3. The apparent K_m of translocator for ADP increased from 2.8 to 6.2 μM in hypothyroid preparations: Mg²⁺ ions raised this to about 20μM. 4. All of these changes in adenine nucleotide translocation were entirely reversed by 15 min after a single intravenous near‐physiological dose of triiodothyronine.