Histidine Absorption across Apical Surfaces of Freshwater Rainbow Trout Intestine: Mechanistic Characterization and the Influence of Copper

Histidine Absorption across Apical Surfaces of Freshwater Rainbow Trout Intestine: Mechanistic... The essential amino acid histidine performs critical roles in health and disease. These functions are generally attributed to the amino acid itself, but could also be mediated by a positive effect on trace element bioavailability. Mechanistic information regarding the absorption of histidine across the gastrointestinal tract is essential for understanding the interplay between amino acid and mineral nutrients and the implications of these interactions for nutrition and toxicology. Using intestinal brush-border membrane vesicles obtained from freshwater rainbow trout, absorption of histidine over the range 0.78–780 μm was found to be saturable, with a maximal transport rate (J max) of 9.1 ± 0.8 nmol mg protein−1 min−1 and a K m (histidine concentration required to reach 50% of this level) of 339 ± 68 μm. Histidine uptake was highly specific as 10-fold elevated levels of a variety of amino acids with putative shared transporters failed to significantly inhibit uptake. Elevated levels of d-histidine, however, impaired uptake of the natural l-isomer. The presence of “luminal” copper (8.3 μm) significantly increased both the J max and K m of histidine transport. This suggests that chelated copper–histidine species cross the brush-border epithelium through transport pathways distinct from those used by histidine alone. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Histidine Absorption across Apical Surfaces of Freshwater Rainbow Trout Intestine: Mechanistic Characterization and the Influence of Copper

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Publisher
Springer-Verlag
Copyright
Copyright © 2008 by Springer Science+Business Media, LLC
Subject
Life Sciences; Human Physiology ; Biochemistry, general
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-007-9088-y
Publisher site
See Article on Publisher Site

Abstract

The essential amino acid histidine performs critical roles in health and disease. These functions are generally attributed to the amino acid itself, but could also be mediated by a positive effect on trace element bioavailability. Mechanistic information regarding the absorption of histidine across the gastrointestinal tract is essential for understanding the interplay between amino acid and mineral nutrients and the implications of these interactions for nutrition and toxicology. Using intestinal brush-border membrane vesicles obtained from freshwater rainbow trout, absorption of histidine over the range 0.78–780 μm was found to be saturable, with a maximal transport rate (J max) of 9.1 ± 0.8 nmol mg protein−1 min−1 and a K m (histidine concentration required to reach 50% of this level) of 339 ± 68 μm. Histidine uptake was highly specific as 10-fold elevated levels of a variety of amino acids with putative shared transporters failed to significantly inhibit uptake. Elevated levels of d-histidine, however, impaired uptake of the natural l-isomer. The presence of “luminal” copper (8.3 μm) significantly increased both the J max and K m of histidine transport. This suggests that chelated copper–histidine species cross the brush-border epithelium through transport pathways distinct from those used by histidine alone.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jan 23, 2008

References

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