Liver Cell Proliferation in X-Irradiated Rats After Single and Repetitive Partial Hepatectomy

The behavior of hepatic tissue of previously irradiated rats, after repeated stimuli to cell proliferation, has been studied. Less than 10 percent of the mitoses in regenerating liver of nonirradiated rats was visibly aberrant, whereas 75 to 80 percent of the mitoses in postirradiation animals was abnormal. These abnormal mitoses persisted in the same frequency after repeated partial hepatectomies and for as long as 17 weeks after the initial exposure to X ray, in spite of the fact that the partial hepatectomies resulted in extensive hepatic-cell replacement. Regeneration of livers of the irradiated animals was characterized by (a) tissue-mass restoration equal to the controls, (b) significant decrease in the peak mitotic index (50 to 60% below values in nonirradiated controls), and (c) a significant decrease in parenchymal cell numbers per microscopic field, i.e., larger parenchymal cells.