Thioacetamide, administered in a dose of 50/mg/kg for 9 days, produced a profound effect on the distribution and labeling of ribonucleic acid (RNA) of the rat liver. The amount of p-RNA (released by phenol into the aqueous phase) and r-RNA (which remained in the phenol), was increased two- to threefold in the nuclei. In the nucleoli, the amount of p-RNA was doubled, and the r-RNA was increased by a factor of 3.5. The amount of mitochondrial and microsomal RNA was correspondingly decreased, but the p-RNA of the cytoplasmic sap was increased. Thioacetamide suppressed the incorporation of orotic acid-2-C14 into the p- and r-RNA of the nuclei. As measured by specific activity, the labeling of nucleolar p-RNA was unchanged by thioacetamide. The labeling of the r-RNA of the nucleoli was suppressed by 30 per cent at early time points.


Supported by grants from the U.S. Public Health Service, Jane Coffin Childs Fund, the American Cancer Society, and the Anna Fuller Fund.

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