Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/16/2000
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Zinc homeostasis and normal plasma zinc concentrations are maintained over a wide range of intakes. To identify the homeostatic response to severe zinc depletion using a compartmental model. Stable isotopic tracers of zinc were administered to five men at baseline (12.2 mg dietary Zn mg/d) and after five weeks of acute depletion (0.23 mg/d). A compartmental model of zinc metabolism was developed using the tracer and plasma, urinary, and fecal mass data collected over a 6-d period. Plasma zinc concentration fell an average of 65% after five weeks of depletion. The model predicted that fractional zinc absorption (FZA) increased from 26% to essentially 100%. The rate constants for zinc excretion into the urine and the gastrointestinal tract decreased 96 and 74%, respectively. The rate constants describing the distribution kinetics of plasma zinc did not change significantly. When zinc depletion was simulated using our average mass model of zinc metabolism at baseline, the only parameter change that accounted for the observed fall in plasma zinc concentration was a 60% reduction in the rate constant for zinc release from the most slowly turning over zinc pool. The large changes in zinc intake, excretion, and absorption, even when taken together, only explained modest reductions in plasma zinc mass. Kinetic analysis with a compartmental model suggest that the profound fall in plasma zinc concentration after five weeks of severe depletion is mainly due to a comparable decrease in the rate of zinc release from the most slowly turning over body zinc pool.