The effects of bile salt and raw bile on the intestinal absorption of micellar fatty acid in the rat in vitro.

1. The uptake, esterification and transport of [(14)C]oleic acid were studied using sacs of rat everted small intestine incubated in 25 ml. of a buffered mixture of sodium taurocholate, glyceryl mono-oleate and (14)C-labelled oleic acid in micellar form.2. Intestine obtained from bile fistula rats (bile duct cannulated 48 hr previously) showed elevated rates of (14)C uptake into the tissue total lipid compared with sham-operated controls.3. Nearly all of the excess (14)C uptake in the bile fistula group was in the form of free fatty acid. Both groups showed similar rates of [(14)C]oleic acid incorporation into tissue triglyceride and also similar, though small, amounts transported into the serosal fluid.4. In further experiments using intestine from bile fistula rats the addition of 1 ml. of fresh rat bile to the incubation mixture reduced the (14)C uptake to approximately control levels. The addition of 2-3 ml. of fresh bile similarly reduced the uptake and increased (14)C incorporation into the triglycerides of mucosal tissue and serosal fluid.5. These responses were not entirely the result of the bile salts contained in fresh bile since increasing the taurocholate concentration per se caused uptake, esterification and transport all to increase. In the presence of the higher taurocholate concentration the addition of fresh bile still caused a decrease in (14)C uptake.6. There was no significant effect of either fresh bile or taurocholate on the transport of the 3-O-methyl analogue of D-glucose under comparable conditions.7. It is concluded that raw bile contains one or more components other than bile salts which may be important in determining fatty acid absorption.