Enhancement of jejunal absorption of conjugated bile acid by neurotensin in rats

Background & Aims: Release of neurotensin (NT) from intestines is markedly stimulated by ingested fat, and NT may facilitate lipid digestion and absor ption through various actions that are not fully understood. Our recent fin ding that NT stimulates hepatic output of bile acids only when bile deliver y to the intestine is maintained has led us to investigate the effects of N T on bile acid absorption in the rat small intestine. Methods: We measured the effects of intravenous infusion of NT (3-10 pmol kg(-1) min(-1)) on bil iary recovery of H-3-taurocholate (H-3-TC) and H-3-cholate administered int o proximal and distal intestines or into isolated intestinal segments in si tu in biliary fistula rats. To further understand the underlying mechanisms involved, the effects of NT on intestinal absorption of H-3-D-glucose, H-3 -leucine, C-14-antipyrine, and Cr-51-EDTA were investigated by monitoring t he absorption of radioactivity into superior mesenteric venous blood, Resul ts: Infusion of NT, at doses that caused near physiologic increases in bloo d NT levels, increased biliary recovery of H-3-TC from the jejunum (3.4-fol d) and ileum (1.7-fold), but did not enhance absorption of H-3-cholate. NT also facilitated transcellular uptake of H-3-glucose and H-3-leucine and in creased paracellular uptake to 51Cr-EDTA and H-3-mannitol, but did not alte r the absorption rate for C-14-antipyrine. Conclusions: These results indic ate that NT can exert a facilitative effect on intestinal bile acid absorpt ion and return to liver. This effect of NT may involve increases in paracel lular absorption and carrier-mediated transport by mechanisms not yet ident ified.