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.