Effects of thyroid hormones on the bypasses of the antimycin A block in the bc1 complex of rat liver mitochondria

Adverse effects of reverse triiodothyronine on cellular metabolism as assessed by 1H and 31P NMR spectroscopy

Effects of 3,3',5'-triiodothyronine (rT3) in connection with 3,3',5-triiodothyronine (T3) on 3T3 cells were studied in vitro by means of 1H and 31P NMR spectroscopy. In the cells incubated with 5 nM T3 for 3 h at pH 7.4, the ATP/ADP ratio was elevated from 6.9 to 8.4, whereas it was reduced to 6.1 in cells incubated with rT3. When the cells were incubated at pH 6.7, the ATP/ADP ratio was reduced to 6.6 and 5.2 at 1 and 2 h, respectively. In the presence of 5 nM of T3, however, the ratio was maintained above the control level. A 1-h preincubation with rT3 dramatically augmented the reductions caused by elevated acidity. These reductions were completely reversed when the cells were incubated with T3.