Sequential observation was made to detect the phenotypic change of mast cells during the process of dimethylaminoazobenzene-induced hepatocarcinogenesis in rats by cytochemistry, immunocytochemistry and electron microscopy. The number of mast cells in the liver tissues increased in various extent 4 weeks following the exposure to carcinogen. The increasing tendency was speeded up as time proceeded. At the 16th week, the number of mast cells reached to seven times as that in the normal rats. The mast cells appeared in the early stage of carcinogenesis were connective tissue mast cells (CTMC). From the 16th week on, mucosal mast cell (MMC) could be detected in some animals, but its number was much less than that of CTMC. In the late stages of experiment, the number of mast cells increased markedly, which showed positive reaction by ARMCP I and ARMCP II staining respectively and were to be brown or blue in color by combined Alcian blue. PAS. ABC staining. At the same time, an inter mediate type of mast cell between MMC and CTMC, light brown in color was also observed. Immunocytochemically, these cells presented ARMCP II positive reactivity. In various kinds of liver tumours formed at 26th week, mast cells occurred in a quite varying amount in different animals. No relationship was found between the amount of mast cells and the cell type or differentiation of the tumours, while the phenotypic distribution of mast cells was closely correlated with the histological type. The development and ultrastructural characterization of mast cells in the portal tracts and sinusoids were also investigated.
Animals Liver