[Thyroxine induction of aminotransferases in subcellular fractions of rat heart]

Administration of thyroxine toxic doses to rats results in a considerable increase in the alanine aminotransferase and aspartate aminotransferase activity in nuclear, mitochondrial and supernatant fractions of the rat heart. The hormone action is more pronounced in the mitochondrial fraction. A simultaneous administration of thyroxine and actinomycin D decreases the hormone effect in case of nuclear and supernatant enzymes. The enzymes of mitochondrial fractions do not change after actinomycin D injection. It is possible to suggest that in mitochondria there occurs a synthesis of some enzymes.