Characterization and effect of phospholipid on bile acid absorption by villi isolated from hamster small intestine.

The effects of phospholipid on absorption of bile acids by hamster small intestine were studied to determine if this compound inhibits absorption of bile acids. Absorption of taurocholic and cholic acids was studied using a new in vitro technique that relates uptake rates to the weight of the villi present on the intestinal sample rather than to the weight of the entire segment of intestine used for the study. This procedure removes from consideration various components of the intestinal wall that are not directly involved with the absorptive process. Using radioactive techniques absorption of each type of bile acid was determined over a broad range of concentrations both in the presence and absence of phospholipid in the incubation medium. Absorption of taurocholic acid by villi from jejunum was determined to be a passive process, as previously reported by others. Villi from ileum absorbed both bile acids by an apparent active process when initial concentrations of bile acids were below 2.0 mM. Above this concentration bile acid absorption by the ileum appeared to be mainly passive. Phospholipid was found to inhibit bile acid absorption by ileum when initial bile acid concentrations were moderately high. However, at low substrate concentration, phospholipid has no appreciable effect on bile acid transport.