Effects of Bile Acids, Lecithin, and Monoolein on Amino Acid Absorption from the Human Duodenum

Abstract

The effects of bile acid, lecithin and monoolein (MO) on essential amino acid (EAA) absorption from the human duodenum were determined. It was found that methionine was absorbed at the most rapid rate while isoleucine, leucine and valine were absorbed slightly less rapidly and lysine and threonine at the slowest rates; duodenal EAA absorption rates are very similar to previously reported rates for jejunal absorption of EAA; taurocholate (TC) and taurodeoxycholate significantly depressed EAA absorption; and although emulsified MO had no significant effect on EAA absorption, the addition of MO or lecithin to the EAA + 10 mM TC perfusion mixture restored EAA absorption to normal. How bile acids inhibit EAA absorption and how lecithin and MO abolish this inhibition are not known. It is postulated that when either lecithin or MO is present, less bile salt is available to act at the surface membranes of intestinal cells, disruption of cell membranes is prevented and EAA absorption proceeds normally.