Liver cells in suspension are shown to incorporate several RNA precursors into their RNA. 2. The incorporation of [(32)P]phosphate and [(14)C]adenine into the RNA of the cell suspension is usually of the same order as that in the perfused (or unperfused) liver slices. However, the initial lag in the incorporation of adenine into the RNA of the cell suspensions is much longer than that obtained for the tissue slices, and the optimum incorporation of adenine in the former, unlike that in the latter, needs exogenous glucose and probably a high concentration of phosphate. 3. The cell suspensions also differ from the tissue slices in being unable to incorporate [(14)C]orotic acid into their RNA, and resemble tumour tissues in incorporating uracil into their RNA at a rate significantly higher than that obtained with the tissue slices. 4. The above differences in the metabolic behaviour of liver-cell suspensions and tissue slices are considered to be due to the different levels of organization of the liver cells in the two tissue preparations.
