Copper absorption inhibition by histidine is potentiated by cobalt

Copper (Cu) absorption is inhibited by excess zinc (Zn) and histidine (His), presumably by metallothionein (MT) induction. Since cobalt (Co) also stimulates MT synthesis, the authors tested the effects of intestinal Co exposure on Cu absorption in the absence of presence of His, in rats. Using jejunal perfusion technique, Cu was perfused at 31.5 uM. Addition of Co at 0.5 and 1.0 mM did not alter Cu absorption in the absence of His. When His was present at 2 mM, Cu absorption decreased from a baseline of 131.8 {plus minus} 9.0 pmol/min {times} cm to 85.5 {plus minus} 11.2, 48.8 {plus minus} 4.3 and 44.3 {plus minus} 6.0. This reduction was associated with an inhibition of net water absorption: 1.23 {plus minus} 0.09 uL/min {times} cm; 0.45 {plus minus} 0.09; 0.33 {plus minus} 0.09; 0.20 {plus minus} 0.09. Cu retained by the perfused intestinal segment was not affected by the presence of either His or Co. Intestinal MT did not change by exposure to Co plus His. These data indicate that the simultaneous presence of an amino acid (His) with a competing cation (Co) has a potentiating inhibitory effect on Cu absorption, possibly associated with the transmembrane passage of aminomore » acid-metal chelates.« less