Influence of thyroid hormone treatment on the respiratory activity of cerebral mitochondria from hypothyroid rats. A critical re-assessment.

Effects of treatment with thyroid hormones L-3,5,3'-tri-iodothyronine (T3) and L-thyroxine (T4) on oxidative energy metabolism in cerebral mitochondria from hypothyroid adult rats were examined. It was observed that T3 and T4 stimulated respiratory activity in a substrate-specific and dose-dependent manner. The results also suggest that the synthesis of cytochrome aa3 and of cytochrome c may be dependent on both T3 as well as T4 whereas higher concentrations than normal of T3 and T4 may have a catabolic influence on cytochrome b content.