In an attempt to elucidate the chronic pathological lesions induced by aflatoxin B₁, the present study in male Sprague-Dawely rats was undertaken to evaluate the relation between the light microscopic changes of the liver and the electron microscopic changes.
The control group animals were fed basal diet. The experimental group animals were fed the powdered basal diet containing 1 ppm aflatoxin B₁ for 10 months with three times administration of afiatoxin B₁(lmg/kg) by gastric tube.
The aflatoxin B₁ was dissolved in peanut oil(1mg aflatoxin B₁ to 1ml peanut oil).
For demonstration of iron exculding foci, the animals were iron loaded by subcutaneous injection of 5mg iron dextran/40gm body weight, in the inguinal region with the sides alternated two times per week for 2 weeks prior to killing.
All animals were sacrificed after 10 months.
The results on morphologic changes were as follows：
1. Light microscopically, the normal hepatic lobular structure was distorted, and replaced by the basophilic nodules, eosinophilic nodules, vacuolated nodules and hyperplastic foci.
2. Light microscopically, the hyperplastic foci were distinct from the discrete nodules often compressing the surrounding parenchyma. There was a decrease in the intensity of the PAS staining in the nodules, compared with that of the control.
3. Electron microscopically, the nodular and hepatocellualr carcinoma cells showed variation in the size and form of mitochondria, shortened or depleted microvilli, proliferation or blebbing of smooth endoplasmic reticulum, irregular shape nuclei and nuclear membrane, and nucleolar segregation of fibrillar and granular elements, etc.
4. The eosinophilic nodules were distinguished from other lesion by the multiple concentric membranous bodies in the cytoplasm of nodular cells. These cytoplasmic structures were also present in some hepatocellular carcinoma cells.
5. Grossly, the incidence of hepatoma was 3.3％(1 rat), and microscopically the early lesion of hepatocellular carcinoma were observed in 2 rats (6.6％), which were linked with eosinophillic nodules.
6. Iron excluding foci were noted at the nodules and hepatocelluar carcinoma lesions, while iron was diffusely pigmented in the control.
The observations provided some evidence suggesting that the eosinophilic nodules, rather than the basophilic nodules, may play a role in the development of malignancy in the rat liver.
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