EFFECT OF BILE ON THE INTESTINAL BILE-ACID BINDING-PROTEIN (I-BABP) EXPRESSION - IN-VITRO AND IN-VIVO STUDIES

Enterocytes actively transport bile acids from the ileal lumen to the portal blood, This physiological process greatly contributes to mainta ining the bile acid homeostasis. However, little is known about the mo lecular mechanisms involved in this transport system, The effect of bi le on gene expression of the intestinal bile-acid binding protein (I-B ABP) expressed in the enterocytes was studied in vivo, using the by-pa ss method, and in vitro, using organ culture of ileum explants and Cac o-2 cell line, The low cytosolic I-BABP concentration and I-BABP mRNA level found in diverted ileum was totally recovered when bile was adde d in the heal lumen. Northern blot analysis of the ileal explants reve aled a dose-dependent increase in the I-BABP mRNA in the presence of b ile. In Caco-2 cells, the I-BABP transcript was dramatically increased in the presence of human bile while it was undectable in the control cultures, These data offer the first evidence that biliary components regulate the I-BABP gene expressed in the enterocytes.