Development of in Vivo Cecal and Colonic Calcium Fluxes in Growing Rats 1

Summary

Small intestinal calcium transport correlates with body growth rates and declines with increasing age, but effects of age on calcium transport by large intestine have not been examined. We studied groups of rats at mean ages of 4, 7, and 10 weeks. Cecal and colonic net calcium absorption and unidirectional fluxes were measured by in situ luminal perfusion of 1.6 mM Ca. Rates/g dry tissue declined with age in both segments, except for colonic plasma-to-lumen flux. Rates per segment reflected progressive tissue growth; lumen-to-plasma fluxes and cecal net absorption increased slightly, colonic net absorption was maintained, and colonic plasma-to-lumen flux doubled. Thus, in contrast to small intestine, total contribution of cecum to calcium homeostasis increases slightly with age; the colon may be responsible for the increasing loss of fecal endogenous calcium with decreasing body growth reported by isotopic studies.