NEITHER INTESTINAL SEQUESTRATION OF BILE-ACIDS NOR COMMON BILE-DUCT LIGATION MODULATE THE EXPRESSION AND FUNCTION OF THE RAT ILEAL BILE-ACID TRANSPORTER

The regulatory responses of bile acid (BA) transport in the terminal i leum to perturbations in BA homeostasis are complex, and conflicting r esults have been reported by different investigators. These studies we re designed to examine the response of this system to a reduction in i leal bile salt concentrations at both a functional and molecular level . Common bile duct ligation (BDL) or feeding of a novel bile acid-bind ing compound, GT31-104HB, for 7 days were used to reduce ileal apical membrane bile salt flux. Apical bile acid transport function was asses sed by examining sodium-dependent uptake of [H-3]-taurocholate (TC) in to brush border membrane vesicles (BBMV). Expression of the apical sod ium-dependent bile acid transporter (ASBT) and the ileal lipid-binding protein (ILBP) were assessed by Western blotting with quantitation us ing [I-125]-labeled secondary antibody and a phosphorimager, Neither c ommon BDL nor intestinal sequestration of BA led to a change in ileal bile acid transport function or the expression of the ASBT or the ILBP , These results indicate that a reduction in presentation of bile salt s to the apical surface of the terminal ileum does not modulate the ex pression of the genes involved in their transport.