Localization of alpha-fetoprotein by immunofluorescent method during induction of rat liver tumors by 3'-methyl-4-dimethylaminoazobenzene.

Localization of alpha-fetoprotein (alpha-FP) has been followed in hepatal tissue and tumors during induction of primary hepatomas with the aid of 0.12% 3'-Me-DAB (3'-methyl-4-dimethylammoazobenzene) in Wistar rats. The indirect immunofluorescence method was used for the localization of alpha-FP positive cells. During the course of carcinogenesis, alpha-FP in serum was detected by means of the crossing over immunoelectrophoresis. This study has yielded the following results: Alpha FP positive cells resembling small hepatocytes occurred dispersed and in groups beginning with the 5th week of a carcinogenic diet until the appearance of tumors. No alpha-FP positive oval cells have been found. Alpha-FP positive cells were always found in rats with alpha-FP positive serum, but they were rarely present in rats with alpha-FP negative serum. From the 10th week, tumors of the cholangiohepatoma type began to be formed in which variously scattered alpha-FP positive cells of the type of small hepatocytes were present, with the serum being negative. Between week 14 and 21 hepatoma nodules began to be formed. At week 21 frequent alpha-FP positive cells close to normal hepatocytes were observed both singly and in groups. These are considered to be the sites of developing tumor nodules. In all the hepatoma nodules, the number of positive tumorous cells and the intensity of fluorescence proved to be directly proportional to alpha-FP concentration in serum.