The ultrastructural features of aflatoxin B1-induced lesions in the rat liver.

Hepatocellular carcinoma was induced in rats by administering aflatoxin B1 (AFB1) for 6 weeks. Malignant tumours were preceded by foci and nodules of altered hepatocytes. The ultrastructural characteristics of the nodular lesions have been studied and compared with those of the hepatocellular carcinoma cells. Alterations in the endoplasmic reticulum, junctional complexes and nuclei were common to both the basophilic and eosinophilic nodular cells and the carcinoma cells. These most likely represent hyperplastic changes rather than malignant alterations. The eosinophilic nodules were distinguished from other lesions by the abundance of concentric, membranous whorls in the cytoplasm of nodular cells. These cytoplasmic structures were also present in some hepatocellular carcinoma cells. The observations provided further evidence suggesting that the eosinophilic nodule, rather than the basophilic nodule, may play a role in the development of malignancy in the rat liver.