Intestinal absorption of bile salts in the rat

Studies of taurocholate and cholate-C14 absorption by slices of rat intestine reveal that an active absorptive mechanism obeying Michaelis-Menten kinetics is present in the ileum but absent in other portions of the gut. Following 1 day of bile duct cannulation, the in vitro absorption of bile salts was enhanced two- to three-fold. The normal tissue concentration of bile salts in the ileum reached 1.3 µm and in the jejunum 0.35 µm/g tissue water. The presence of endogenous bile salts resulted in inhibition of subsequent ileal active absorption competitively suggesting the existence of a common receptor site for mucosal bile salt absorption. Active absorption was dependent on sodium concentration and inhibited by potassium. The significance of these results is discussed.