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Populations of Rat Liver Parenchymal Cells with Different Patterns of Ribonucleic Acid Synthesis during Azo-Dye Carcinogenesis

Biology Branch, National Cancer Institute, Bethesda, Maryland 20014

"Preneoplastic" parenchyma of liver nodules produced by 3'-methyl-4-dimethylaminoazobenzene could be distinguished as hyperbasophilic and basophilic cells. Ribonucleic acid synthesis in these cells was studied 3 hours after the injection of uridine-³H. Autoradiographic data showed that ribonucleic acid syntheisis in the hyperbasophilic cells was 70 percent higher than the basophilic cells and 50 percent greater than the liver parenchyma of the control rats. A similar difference was also evident in the labeling pattern of the cytoplasm, chromatin, and nucleolus. After partial hepatectomy, ribonucleic acid synthesis in the hyperbasophilic cells was increased 60 percent at 12 hours; in the basophilic cells, the same biosynthetic activity was stimulated only up to 29 percent. The hyperbasophilic cells were 50 percent more responsive to the stimulus of partial hepatectomy than the basophilic cells. In the hyperbasophilic cells the increased radioactivity in the chromatin was accompanied by a similar rise of cytoplasmic labeling. The increased uridine-³H uptake in the chromatin of the basophilic cells failed to show an enhancement of the cytoplasmic labeling. In intact liver, one population of the "preneoplastic" parenchyma was hyperactive in ribonucleic acid synthesis while the other was only moderately active. Partial hepatectomy produced different patterns of responsiveness of the ribonucleic acid synthetic processes in these cell populations. Variable basophilic properties of the "preneoplastic" parenchyma thus might be due to the different rate of ribonucleic acid synthesis of these cells. Significance of these findings concerning the proliferative potential of the hyperbasophilic and basophilic cells was discussed.

¹ Present address: Institute for Cellular Research, Department of Zoology, University of Nebraska, Lincoln, Nebraska 68503.

² Requests for reprints should be sent to Dr. Richard S. Yamamoto, Carcinogen Screening Section, Biology Branch, National Cancer Institute, Bethesda, Maryland 20014.

Received 6/27/67. Accepted 10/29/67.