The effect of age on mitotic activity in rat oral epithelium

One hundred and thirty eight male white albino rats were used in this study. Serial sections were prepared of the palate, tongue, gingiva and ear and were stained with hematoxylin and eosin. The experiment utilized one group of rats aged 3 months and another at 15 months. At 3 hour inter‐ vals during a 24 hour period 3 rats from each group received an injection of colehicine and were sacrificed 3½ hours later. Counts of arrested metaphases demonstrated that the mitotic activity of young and old animals were dmilar or tended to decrease with age. In 2, 3, 6, 15 and 25 month old rats no relationship was found between the number of nucleated cells in the various epithelia and the age of the animals. Using colchicinized rats and non‐treated rats the duration of the mitotic phase was estimated in tongue epithelium of young and old animals. The result of this ex‐periment indicated that the duration of the process of cell division tends to increase with age. The results of this study favour the opinion that mitotic activity decreases with increasing age.