Immunofluorescent study on alpha-fetoprotein-producing cells in the early stage of 3'-methyl-4-dimethylaminoazobenzene carcinogenesis.

The study was carried out to identify alpha-fetoprotein (AFP)-producing cells in the hepatic tissue by immunofluorescent antibody techniques during the early stage of 3'-methyl-4-dimethylaminoazobenzene ingestion. After 1 to 3 weeks, cells fluorescent to AFP were undetectable in cholangiolar cells ("oval cells") and also in degenerated megalocytic hepatocytes. After 4 to 7 weeks AFP appeared in rat sera, and "transitional cells" and small hepatocytes proliferated markedly in the periportal areas of hepatic lobules. AFP was exclusively detected in the majority of the transitional cells and a small portion of the small hepatocytes. Some fluorescent cells appeared in small groups, and others were randomly distributed in the periportal areas. The typical oval cells and the megalocytic hepatocytes were not fluorescent. When AFP in sera became undetectable, the regenerated hepatocytes matured considerably and were not brightly fluorescent. In the hepatic tissue, where AFP-producing cells were observed by fluorescent antibody technique, hematopoietic cells were frequently observed but they were not fluorescent.