Gary W. Evans
Apr 27, 2009
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Influential Citations
58
Citations
Quality indicators
Journal
Nutrition reviews
Abstract
The studies reviewed suggest that zinc absorption proceeds as follows: in the exocrine cells of the pancreas the metabolism of tryptophan produces picolinic acid which is secreted into the lumen of the intestine. In the lumen, picolinic acid coordinates with Zn to form a complex which facilitates the passage of Zn through the luminal membrane, across the absorptive cell and through the basolateral membrane of the cell. Alternatively, at the basolateral membrane receptor ligands may coordinate Zn which is then transferred to transferrin. In man and animals consuming diets with physiological amounts of Zn, the quantity of Zn transported across the absorptive cell is directly related to the availability of picolinic acid. The availability of picolinic acid depends on the amount of dietary tryptophan, pyridoxine and cations which compete with Zn for coordination with picolinic acid. Inborn errors of metabolism which affect the conversion of tryptophan to picolinic acid also cause impaired Zn absorption.