Subcellular localization of alpha-tocopherol and its effect on RNA synthesis in perfused rabbit heart.

3H-tocopherol was administered by perfusion to rabbit hearts and rapidly entered the myocardial cells with an incorporation rate which was more evident inthe alpha-tocopherol deficient hearts than in the control hearts. During perfusion, the labelled alpha-tocopherol was slightly metabolized and 85% of the radioactivity was recovered as authentic alpha-tocopherol. The pattern of alpha-tocopherol distribution showed in both perfused hearts a significant binding of the radioactivity to the nuclei. The vitamin was also retained with high specific labelling in the mitochondria and in a lower degree in the microsomes and soluble fractions. Small amounts of radioactivity was found bound to the myofibrils. The study of the intranuclear distribution of tocopherol has revealed that the tocopherol-binding species were acidic nuclear macromolecules which exhibited characteristics of non-histone chromosomal proteins. Administration of alpha-tocopherol exhibited a positive effect on the stimulation of labelled RNA in the tocopherol-deficient perfused hearts. This was particularly evident at the nuclear level. The intracellular distribution of the vitamin and its ability to stimulate RNA synthesis in heart muscle can suggest a possible role of alpha-tocopherol in the regulation of gene activity.