Interrelation of amino acids and pH on intestinal iron absorption

Abstract

Loops of proximal small intestine of rats were perfused in vivo with Fe59SO4 in phosphate buffer alone or with added glutamine or histidine over 4 pH ranges: 1. 3-2. 0, 2.0-3.5, 5.0-6.5, 7.0-8.0. It was found that in all pH ranges the addition of amino acids effected higher Fe59 activity in blood, liver and carcass than phosphate buffer alone. The lowest pH range (1. 3-2. 0) was not associated with maximal Fe absorption. Maximal Fe absorption occurred in pH range 2. 0-3. 5. Iron absorption decreased with increasing pH beyond this range; however, the Fe59 activity expressed as the ratio of amino acid group to control group increased with rising pH. In other words, the highest pH range decreased Fe absorption to a much lesser extent when the Fe was administered with an amino acid. There was an inverse relationship between the Fe59 activity of the perfused intestinal segments and the other tissues studied. These findings are compatible with the suggestion that the buffering of luminal pH is not the sole mechanism of enhanced iron absorption seen with amino acids, and that amino acids are associated with more rapid transit of luminal Fe into the body.