Growth of carcinogen-altered rat hepatocytes in the liver of syngeneic recipients promoted with phenobarbital.
An improved transplantation system for the study of carcinogen-altered hepatocytes is described. This system, which is based on that reported by Laishes and Farber (Cancer Res., 61: 507-512, 1978), involves the transfer of hepatocytes from male F344 animals to syngeneic adult hosts. Unlike the earlier protocol, the recipient rats were fed phenobarbital (PB) rather than the DNA-reactive agent, 2-acetylaminofluorene. gamma-Glutamyl transpeptidase (GGT)-positive hepatocytes were induced in the donor animals by one of three different hepatocarcinogenic treatment regimens. The recipient rats received 0.05% PB in the diet for 3 wk prior to the cell transfer and were maintained on the PB diet for 2 to 7 mo. Hepatocytes from a male F344 donor rat that had received a 70% hepatectomy and 30 mg of diethylnitrosamine per kg and had been maintained on 0.05% PB for 12 mo formed GGT-positive colonies and hepatocellular carcinomas in both male and female recipients. No GGT-positive colonies were formed when 0.05% PB was omitted from the diet of the recipients. A 70% partial hepatectomy of the recipients at the time of cell transfer was also essential for the development of colonies and tumors. The mean volume of the colonies was 5 times larger in female recipients than in males, occupying 38% of the total liver volume in the females. GGT-positive foci arose in recipient livers that had received hepatocytes from either a male F344 donor rat treated according to the Solt and Farber [Nature (Lond.), 263: 701-703, 1976] selection protocol or a male F344 donor rat that received a 70% hepatectomy and 30 mg of diethylnitrosamine per kg and was maintained on 0.05% PB for 5 mo. The recipient animals were treated with PB which the initial experiments showed was essential for the development of foci. The number and volume of the foci in the recipient varied according to the treatment regimen that the donor rat received. This system provides a method for analyzing the growth regulation of altered foci at various stages of neoplastic development during hepatocarcinogenesis in the rat in the absence of DNA-reactive selection agents.