title: Dysprosium as a nonabsorbable fecal marker in studies of zinc homeostasis.
abstract: BACKGROUND
  Dysprosium is a nonabsorbable rare earth element that has had successful application as a marker for fecal excretion of unabsorbed zinc.
  
  
  OBJECTIVE
  Our goals were 1) to evaluate the efficacy of administering dysprosium with all meals over several days as a method of determining the completeness of fecal collections, 2) to determine the similarity of gastrointestinal transit kinetics and excretion patterns of dysprosium and zinc tracer administered simultaneously over several days, and 3) to evaluate alternative methods of using the data for fecal excretion of orally administered zinc tracer and dysprosium to measure the fractional absorption of zinc.
  
  
  METHODS
  70Zn and dysprosium were administered orally with all meals for 5 consecutive days to 7 healthy, free-living adults consuming a constant diet based on habitual intake. Additional tracers, 67Zn and 68Zn, were administered intravenously. Urine and fecal samples were collected during tracer administration and for 8 d after the last dose. Isotope ratios were measured in urine and feces, and total zinc and dysprosium were measured in fecal samples.
  
  
  RESULTS
  The mean recovery of dysprosium was 101.3 +/- 2.4%. The zinc oral tracer and dysprosium had similar fecal excretory patterns; the correlation coefficient for 70Zn and dysprosium in fecal samples exceeded 0.99 (P < 0.0001) for each subject. Fractional zinc absorption measurements using various dysprosium methods correlated well (r > 0.95) with those from the fecal monitoring and dual-isotope-tracer ratio methods.
  
  
  CONCLUSIONS
  Administration of dysprosium is a useful means of determining the completeness of fecal collections and of measuring zinc absorption.
authors.affiliation: Section of Nutrition, Department of Pediatrics, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
authors.forename: Xiao-Yang
authors.initials: XY
authors.lastname: Sheng
authors.forename: K Michael
authors.initials: KM
authors.lastname: Hambidge
authors.forename: Nancy F
authors.initials: NF
authors.lastname: Krebs
authors.forename: Sian
authors.initials: S
authors.lastname: Lei
authors.forename: Jamie E
authors.initials: JE
authors.lastname: Westcott
authors.forename: Leland V
authors.initials: LV
authors.lastname: Miller
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001682:Biological Availability; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D015930:Diet Records; D004419:Dysprosium / Q000032:analysis; D005243:Feces / Q000737:chemistry*; D005260:Female; D006801:Humans; D007201:Indicator Dilution Techniques; D007262:Infusions, Intravenous; D007408:Intestinal Absorption / Q000502:physiology; D008297:Male; D016482:Urinalysis; D015032:Zinc / Q000032:analysis / Q000378:metabolism / Q000493:pharmacokinetics*; D015033:Zinc Isotopes
chemical_list: D015415:Biomarkers; D015033:Zinc Isotopes; D004419:Dysprosium; D015032:Zinc