Studies on micellar fatty acid uptake by rat intestine in vitro with reference to the role of bile.

1. The uptake and esterification to trigylceride of oleic acid in micellar form was studied in rat intestine in vitro. Sacs of the upper half of the everted intestine taken from bile fistula rats were incubated in a buffered solution containing mono-olein, (14)C-labelled oleic acid and bile salt (sodium taurocholate (NaTch) in concentrations exceeding the critical micellar concentration).2. At 37 degrees C incubation temperature increasing the NaTch concentration enhanced both uptake and esterification. Adding whole rat bile caused uptake to decrease at all NaTch concentrations but had only a slight and variable effect on esterification.3. Lowering the incubation temperature to 0 degrees C suppressed esterification but had no effect on uptake.4. At 0 degrees incubation temperature adding whole bile still decreased fatty acid uptake but had no effect on esterification.5. It is concluded that intestinal fatty acid uptake from micelles is a non-energy requiring process and that a non-bile salt component in bile exists which can suppress this process.6. It is suggested that lecithin may be the non-bile salt component and that it suppressed uptake by interacting either with the micelles or with the epithelial membrane to reduce fatty acid permeability.