Mitotic index in the regenerating liver of tumor-bearing mice.

The onset and the rate of cellular proliferation in the liver regenerating after partial hepatectomy was studied in C3H mice bearing a transplanted mammary carcinoma and in control animals. The presence of the tumor elsewhere in the body resulted in an earlier onset, with an increased mitotic activity in the remaining liver during the period of 30 to 42 hours after partial hepatectomy. The control liver showed the rise in cellular proliferation at 48 hours. The rate of regeneration had the highest point at 48 hours in both the experimental and control animals. At that time, and throughout the rest of the study, the rate was similar in the two groups. The tumor showed a marked decrease in the number of mitoses at 18 hours, but it started rising thereafter and reached presurgery levels at 48 hours.