Effect of Histidine and Certain Other Amino Acids on the Absorption of Iron-59 by Rats

Abstract

Reports in the literature have indicated that several amino acids can increase the absorption of ferrous iron. The objectives of the experiments reported here were to determine if certain amino acids would increase absorption of ⁵⁹Fe supplied in the ferric form and, if so, to investigate the mechanism of action of these amino acids. Of six amino acids tested, histidine and lysine significantly increased ⁵⁹Fe absorption from ligated, in vivo, duodenal segments, whereas glutamine, glutamic acid, methionine, and glycine did not. Further, histidine was not effective if administered intraperitoneally or if put into an intestinal segment adjacent to the one in which ⁵⁹Fe was administered. When histidine was added to an ⁵⁹Fe solution which contained ascorbic acid, it increased absorption over and above that observed with ascorbic acid alone. In all of these studies, histidine increased ⁵⁹Fe uptake only if histidine and ⁵⁹Fe were administered in the same solution. This suggests some direct reaction between iron and histidine and is consistent with the hypothesis that an amino acid-iron chelate is formed and subsequently absorbed. Since histidine is a product of protein hydrolysis in the gastrointestinal tract, it may be involved in the normal absorption of iron.