Tissue Uptake of Zinc in Rats Following the Administration of Zinc Dipicolinate or Zinc Histidinate

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Abstract
Tissue uptake of zinc was determined in rats fed a low zinc diet (< 1 ppm Zn) and an adequate zinc diet (20 ppm Zn) following the intramuscular injection of either zinc dipicolinate (ZnPA2) or zinc histidinate (ZnHis). Significant differences were observed when dietary and treatment effects on zinc uptake were compared in pancreas, duodenum, jejunum, ileum, kidney, and liver. Zinc uptake by the pancreas was higher in rats fed adequate zinc than in rats fed low zinc regardless of which zinc complex was injected, suggesting that the pancreas has a role in zinc excretion. Since ZnHis was more readily taken up than ZnPA2 by the pancreas of rats on the zinc-adequate diet, zinc chelated by histidine may be more readily excreted than zinc chelated by picolinic acid. No differences in zinc uptake were observed in the intestinal segments from rats fed low zinc compared to rats fed adequate zinc. However, in rats fed low zinc, ZnPA2 was more readily taken up than ZnHis by all intestinal segments implying that zinc chelated by picolinic acid may be more available for storage or utilization by the small intestine than zinc chelated by histidine. Also, the ileum had the highest zinc uptake regardless of which zinc complex was injected. Since the ileum has the largest population of Paneth cells, the high zinc uptake observed in this segment of the small intestine suggests a role for Paneth cells in zinc homeostasis.