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This Article Full Text Full Text (PDF) All Versions of this Article: 561/2/525    most recent jphysiol.2004.072389v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Oakley, F Articles by Thomas, A. L Search for Related Content PubMed PubMed Citation Articles by Oakley, F Articles by Thomas, A. L

¹ School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK

The uptake of ⁶⁵Zn by human erythrocytes was investigated in the presence of high (40 mM) and low (5 mM) concentrations of histidine and 0–500 µM cobalt, nickel, manganese and zinc. Varying concentrations of metal mono- and bis-histidine complexes will be formed and the inhibition of ⁶⁵Zn uptake could be correlated with the calculated complex concentrations to investigate competition between metals. For each metal, the calculated concentrations of bis-histidine complex giving 50% inhibition of ⁶⁵Zn uptake were similar at both 5 mM and 40 mM histidine. Manganese–bis-histidine appeared to have a much higher affinity for the binding site than the other metal–bis-histidine complexes, which had similar affinities to each other. Studies of the inhibition of histidine-stimulated ⁵⁴Mn uptake by the addition of manganese confirmed that manganese–bis-histidine does act as a substrate for the transporter in a similar fashion to the other metals studied. In addition, human erythroleukaemic cells (HEL cells) were used as a model for erythroid precursor cells. L-histidine, but not D-histidine, stimulated ⁶⁵Zn uptake in a saturable fashion. The other metals competed with zinc in a similar manner to that seen in erythrocytes, and the affinity for manganese–bis-histidine was much greater than for the bis-histidine complexes of the other three metals. Both the capacity for metal transport per cell, and the affinity of the transporter for the metal–bis-histidine complexes, were much greater in the HEL cells than in the erythrocyte. It is suggested that histidine-stimulated metal transport may play a role in the supply of metals to maturing erythroid cells.

(Received 22 July 2004; accepted after revision 11 October 2004; first published online 14 October 2004)
Corresponding author N. M. Horn: School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK. Email: nmh{at}soton.ac.uk