[Characteristics of synthesized RNA in the isolated and perfused rat liver]

The incorporation of 3H-orotic acid into nuclear and microsomal RNA from isolated perfused rat liver has been studied. The specific radioactivity of nuclear RNA indicates that the efficiency for RNA synthesis in the perfused liver is similar to that of the liver 'in vivo'. In contrast, the microsomal RNA specific radioactivity is well below that observed 'in vivo'. This may indicate a slower transport of the labelled RNA from the nucleus to the cytoplasm. Labelling pattern of total nuclear RNA, nuclear poly(A) containing RNA and microsomal RNA appear to be in line with these assumptions.