Light microscopic autoradiographic study of DNA synthesis in cecal epithelial cells of aging mice

The localization and activity of DNA synthesis of mouse cecal epithelia from prenatal Day 19 embryos to 12-month adults were investigated by light microscopic autoradiography after [3H]-thymidine injection in vivo. The cecal epithelial labeled cells with [3H]-thymidine were located at the lower half of the crypts, and the labeling index (LI) changed with the development of the cecum due to aging. A peak in the LI of absorptive cells was found at embryonic Day 19, but it decreased strikingly at the first postnatal day and then kept an almost constant value until 12 months. The LI of the goblet cells showed the highest value at fetal Day 19, decreased gradually with aging from the first postnatal day, and completely disappeared from 1 month onwards. The basal granulated cells were located only in the base of crypts, and the significant difference of LI was not found from embryonic Day 19 through 12-month adult. The results obtained in this study suggest that there are some differences of DNA synthesis among different kinds of cecal epithelial cells from embryonic stages to postnatal stages as a result of aging.