IN-VIVO ABSORPTION OF CALCIUM-CARBONATE AND MAGNESIUM-OXIDE FROM THE LARGE-INTESTINE IN RATS

This study was conducted to evaluate the ability of the large intestin e to absorb calcium (Ca) and magnesium (Mg) from their sparingly water -soluble salts, and also to determine whether fructooligosaccharides ( FOS) stimulate the absorption of these minerals in rat large intestine in vivo. Rats were fed Ca- and Mg-free diets with and without 5% FOS. An aqueous suspension of CaCO3 and MgO was infused into the stomach v ia a gastric tube or into the cecum via an implanted catheter. Coproph agy was prevented by using wire-mesh anal cups throughout the experime nt so as to exclude the re-ingestion of feces as an oral mineral sourc e. In rats fed an FOS-free diet, the absorption degrees of Ca and Mg i nfused into the cecum were the same as those infused into the stomach. The absorption degree of phosphorus (P) was slightly but significantl y higher in rats with the infusion of Ca and Mg into the cecum than in rats with the infusion of Ca and Mg into the stomach. FOS-feeding inc reased the absorption of Mg to a similar extent in either case of infu sion via cecal and oral routes, while FOS-feeding did not increase the absorption of Ca in rats with infusion of Ca and Mg into the cecum. W e concluded that both CaCO3 and MgO are absorbed in the large intestin e, and we ascertained that the increasing effect of FOS on the absorpt ion of Mg took place mainly in the large intestine.