In an attempt to elucidate the pathological effects of dimethylnitrosamine (DMN) administration following partial hepatectomy (1/3), the present study was undertaken in male Sprague-Dawley rats.
The evidence of hyperplastic nodules, the number and nuclear size of dysplastic cells, and the ratio of liver weight compared to body weight were evaluated, especially emphasizing on the difference among several groups.
Rats were partially hepatectomized and DMN(10mg or 20mg per Kg) was administered at 20 hours or 40 hours after partial hepatectomy, and then weekly injected three times.
Eight weeks after initial DMN injection group of these animals was placed on a diet containing phenobarbital 50mg per 100ml H₂O.
The animals were sacrified on 60, 90 and 120 days after DMN injection.
The results were as follows：
1. The hyperplastic nodules in the DMN treated groups at 20 hours after partial hepatectomy (PH) were more prominent than those of the DMN treated groups at 40 hours after PH.
2. The number of dysplastic hepatocytes increased in the DMN treated groups at 20 hours after PH, compared to those of the DMN treated groups at 40 hours after PH.
3. The hyperplastic nodules and the numbers of dysplastic hepatocytes were more prominent than those of the control, and also proportional to the amount of treated DMN.
4. The average nuclear size of dysplastic cells was much larger (about 1.5 to 1.6 times) than that of the control.
5. The ratio of liver weight compared to body weight in phenobarbital treated groups was much larger than that of no phenobarbital treated groups.
In summary, the result obtained by the present study indicates dimethylnitrosamine(DMN) induced hyperplastic nodules accompained by liver cell dysplasia. The observations provided some evidence supporting that proliferating hepatocytes rose to a peak at the G₁-S border phase and phenobarbital promoted DMN induced liver cell hyperplasia or dysplasia.
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