Effect of Thyroid Hormone on the Mitochondrial DNA and RNA Levels in Rat Cardiocytes

Abstract

Normal rats show levels of heart mitochondrial DNA and RNA (mit-DNA, mit-RNA) which are 0.66 and 18.82 µg/mg of mitochondrial proteins, or 0.15 and 4.35 fg/mitochondrion, respectively. Thyroidectomy reduces such values, while triiodothyronine (T3) treatment effectively restores normal levels of mitochondrial nucleic acids. These findings complete the pattern obtained previously by the authors for the mitochondrial nucleic acids of liver and suggest that T3 also increases the heart mitochondrial DNA and RNA content, probably due to stimulation of the respective mitochondrial polymerases.