Insulin modulates cellular proliferation in developing human jejunum and colon

Several lines of evidence suggest an important role for insulin in the regu latory mechanism of rodent small intestinal development. To investigate its potential implication in human gut, the immunofluorescent localization of insulin receptors (IR) and the influence of insulin (30 mu U or 3 mU/ml) on [H-3]-thymidine incorporation and on lactase and alkaline phosphatase acti vities were studied in fetal jejunum and colon (14-19 weeks). We demonstrat e the early presence of IR, mainly detected in the basolateral portion of e nterocytes and colonocytes along the crypt-villus axis. Insulin increased [ H-3]-thymidine incorporation as well as epithelial labeling indices in cult ured explants from jejunum and colon without affecting enzymic activities. This study establishes, for the first time, that insulin stimulates prolife ration of epithelial cells expressing IR in both segments without affecting brush border hydrolases in the developing human gut.