Long-term cultivation of two diploid epithelial cell lines derived from normal rat liver cells

To obtain a useful rat liver cell line for in vitro carcinogenesis, two rat diploid epithelial cell lines were established from a 7-day-old male rat by the repeated colonial clone method. More than 80% of cells from each cell line have maintained normal diploid karyotype for over 30 months in vitro. The diploid cells were identi. fied as normal diploid karyotype by conventional Giemsa and trypsin. Giemsa techniques. They showed little difference in morphology and growth rate between early and late passages. Without cloning, they tended to be heterogenous in cell morphology, became heteroploid in chromosome and showed increased growth potential with time. Highly heteroploid cells which were derived from one of the lines produced ascites and solid tumors when inoculated into syngeneic rats intraperitoneally. Histologically, the tumors were diagnosed as poorly differentiated hepatocarcinomas. One of these diploid epithelial cell lines in early passage contained some activity of tyrosine transaminase and liver type aldolase and .glycokinase. Therefore, it is suggested that these epithelial cell lines represent liver parenchymal cells.