Transepithelial transport of cholyltaurine by Caco-2 cell monolayers is sodium dependent.
Bile acids are efficiently recovered from the intestinal lumen by a Na(+)-dependent transport process that is localized in the ileal enterocyte brush-border membrane. To establish a cell culture model for this process, we examined the Na+ dependence of cholyltaurine (C-tau; taurocholate) transport across monolayers of differentiated Caco-2 cells grown on permeable filter inserts. Transport of [3H]C-tau was Na+ dependent (> 20-fold stimulation), saturable, and time linear for at least 60 min. The apparent Michaelis constant of [3H]C-tau transport was approximately 65 microM, and the maximal transport rate was approximately 800 pmol.min-1.mg protein-1. Transport of [3H]C-tau in the apical-to-basolateral direction was 17-fold greater than transport in the reverse direction. Lowered incubation temperature, various metabolic inhibitors, and various unlabeled bile acids inhibited [3H]C-tau transport. Caco-2 cells thus transport bile acids in a manner similar to that described for ileal brush-border membrane vesicles and isolated ileal enterocytes and are therefore an appropriate model for studying the molecular basis of ileal bile acid transport.
Chandler
C E
CE
Department of Cardiovascular and Metabolic Diseases, Pfizer Inc., Groton, Connecticut 06340.
Zaccaro
L M
LM
Moberly
J B
JB
D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D001647:Bile Acids and Salts / Q000494:pharmacology; D001692:Biological Transport; D003110:Colonic Neoplasms / Q000378:metabolism* / Q000473:pathology; D004848:Epithelium / Q000378:metabolism / Q000473:pathology; D006801:Humans; D009994:Osmolar Concentration; D012964:Sodium / Q000502:physiology*; D013656:Taurocholic Acid / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics*; D013696:Temperature; D014407:Tumor Cells, Cultured
D001647:Bile Acids and Salts; D013656:Taurocholic Acid; D012964:Sodium