The effect of cytoplasmic factors on protein synthesis in the liver and brain mitochondria of rats with different thyroid states

The purpose of the paper is to define the role of low molecular weight cytoplasmic proteins of peptide nature in the synthesis of young rat liver and brain mitochondrial proteins. The cytoplasmic modulator isolated from the hyperthyroid rat liver was shown to stimulate the synthesis of mitochondrial proteins of the hyperthyroid rat liver. A similar modulator from the hyperthyroid rat brain did not affect the protein-synthesizing apparatus of thyroidectomized rat liver mitochondria. In a cell-free system, containing brain mitochondria of rats with a different thyroid status, the cytoplasmic modulator failed to influence the incorporation of labeled amino acids in mitochondrial proteins. It is assumed that cytoplasmic low molecular weight modulators participate in a differentiated response of different organs to the action of thyroid hormones.