Effect of carbon tetrachloride on carcinogenicity of petasites japonicus and transplantability of induced tumors.

Effect of carbon tetrachloride on the carcinogenicity of the flower stalk of Petasites japonicus was examined in 3 experimental groups of inbred strain ACI rats. Group 1 received 4% petasites diet until termination of the experiment and intragastric administration of CC14, once every 2 weeks, for a total of 15 times. Group 2 received only 4% petasites diet, and Group 3 CC14 and a basal diet. Another group of rats which were fed a basal diet served as a control groups. Both Group 1 and 2 showed the same incidence of hemangioendothelial sarcoma of the liver (6/22). However, the incidence of hyperplastic liver nodules (19/22) and liver cell adenomas (8/22) in Group 1 was significantly higher than in Group 2 (2/22, 0/22). No hyperplastic liver nodules or liver cell adenomas were noted in Group 3. These results indicate that the administration of CC14 probably enhanced the carcinogenic activity of Petasites japonicus in hepatocellular tumorigenesis. Three hemangioendothelial sarcomas of the liver induced in rats in Groups 1 and 2 were subcutaneously transplanted and established as transplantable tumor lines.