The effect of aging on rat liver regeneration.

The effect of age on hepatocyte mensuration and mitotic activity 48 h after partial hepatectomy was investigated in rats. Both age and partial hepatectomy had significant effects upon hepatocyte counts per microscopic field. The number of hepatocytes per microscopic field declined with age in the control groups of different advancing ages and in the experimental groups of advancing ages. There was essentially no mitotic activity in the livers of the control groups. However, mitotic counts were greatly increased in livers from those animals that were partially Hepatectomized; the increase in mitotic activity in the 13-month-old animals was double over that observed in both the very young and the very old.