Age-related cell proliferation and apoptosis in the kidney of male Fischer344 rats with observations on a spontaneous tubular cell adenoma

Cell proliferation rate and apoptosis were examined in archival kidneys fro m young, middle-aged, and old male F344 rats. Immunohistochemical expressio n of proliferating cell nuclear antigen (PCNA) and apoptosis were quantifie d in the same cell populations of the proximal tubule epithelium. A total o f 79 kidneys from 40 rats were examined. There was a progressive increase i n cell proliferation rates in rats from 4 and 6-10 months of age. In 23-mon th-old rats, proliferative activity appeared to be reduced. No age-related variations in apoptotic indices were found. One of the 16 rats aged 23 mont hs had a tubular cell adenoma. In the tumor-affected kidney, cell prolifera tion rate was dramatically higher than in the contralateral kidney as well as in all the other kidneys examined. This high proliferative activity was not balanced by variation in cell death.