Cellular kinetics of gastrointestinal mucosa, with special reference to gut endocrine cells

After 3H-thymidine autoradiography was introduced to the study of cellular kinetics, the epithelial cells of the gastrointestinal mucosa have been examined extensively with regard to their kinetic behavior. After reviewing the knowledge on the kinetics of different epithelial cells in the stomach and small and large intestine, this article concentrates on the origin, differentiation and turnover of gut endocrine cells which have been under much controversy. Autoradiographic and other investigations of EC cells support the view that these cells are not neuroectodermal in origin, but differentiate from an immature type of gut epithelial cells. We investigated the kinetics of the antral G cells in the hamster, G cells and S cells in the rat duodenum by the combined utilization of 3H-thymidine autoradiography with immunohistochemistry, and confirmed that these cells are derived from the same precursor cells as the other mucosal cells of the gastrointestinal tract. The half-life of the antral G cells was estimated at 10-15 days, while the turnover time of the G cells and S cells in the duodenum were calculated at 3-4 days and 2 days, respectively. These data also support the belief that gut endocrine cells originate from the endoderm. Histopathological alterations such as antral gastritis and intestinal metaplasia, as well as vagal denervation, were shown to influence the population of the antral G cells in man and the hamster. This supports the view that intrinsic and extrinsic stimuli might alter the kinetics of gut endocrine cells.