In vivo cortisol action on RNA synthesis in rat liver nuclei and mitochondria.

Abstract

VARIOUS mechanisms have been proposed for the action of hormones in cells. One is a cytoplasmic mechanism involving mitochondria1,2; a second implies that cytoplasmic protein receptors act as sites3 for the hormone action; a third proposes that the nuclei act as a primary site for hormone action4,5. We now demonstrate that cortisol, when used for brief periods and in physiological doses, increased the RNA polymerase activity of rat liver mitochondria. In these conditions nuclear RNA synthesis was not affected. Hormone treatment for longer periods or treatment with large doses for short time periods increased the nuclear RNA polymerase activity and suppressed the mitochondrial enzyme.