Enhancement of Jejunal Absorption of Conjugated Bile Acid by Neurotensin in Rats

Abstract

Release of neurotensin (NT) from intestines is markedly stimulated by ingested fat, and NT may facilitate lipid digestion and absorption through various actions that are not fully understood. Our recent finding that NT stimulates hepatic output of bile acids only when bile delivery to the intestine is maintained has led us to investigate the effects of NT on bile acid absorption in the rat small intestine. We measured the effects of intravenous infusion of NT (3-10 pmol x kg(-1) x min(-1)) on biliary recovery of (3)H-taurocholate ((3)H-TC) and (3)H-cholate administered into proximal and distal intestines or into isolated intestinal segments in situ in biliary fistula rats. To further understand the underlying mechanisms involved, the effects of NT on intestinal absorption of (3)H-D-glucose, (3)H-leucine, (14)C-antipyrine, and (51)Cr-EDTA were investigated by monitoring the absorption of radioactivity into superior mesenteric venous blood. Infusion of NT, at doses that caused near physiologic increases in blood NT levels, increased biliary recovery of (3)H-TC from the jejunum (3.4-fold) and ileum (1.7-fold), but did not enhance absorption of (3)H-cholate. NT also facilitated transcellular uptake of (3)H-glucose and (3)H-leucine and increased paracellular uptake to (51)Cr-EDTA and (3)H-mannitol, but did not alter the absorption rate for (14)C-antipyrine. These results indicate that NT can exert a facilitative effect on intestinal bile acid absorption and return to liver. This effect of NT may involve increases in paracellular absorption and carrier-mediated transport by mechanisms not yet identified.