title: Biological fractionation of lead isotopes in Sprague-Dawley rats lead poisoned via the respiratory tract.
abstract: OBJECTIVE
  It was considered that lead isotope ratios did not change during physical, chemical, or biological processes. Thus, lead isotope ratios have been used as fingerprints to identify possible lead sources. However, recent evidence has shown that the lead isotope ratios among different biological samples in human are not always identical from its lead origins in vitro. An animal experiment was conducted to explore the biological fractionation of lead isotopes in biological systems.
  
  
  METHODS
  24 male Sprague-Dawley (SD) rats were divided into groups that received acute lead exposure (0, 0.02, 0.2, or 2 mg/kg body weight of lead acetate) via the respiratory route every day for 5 days. Biological samples (i.e., blood, urine, and feces) were collected for comparison with the lead acetate (test substance) and the low-lead animal feed (diet) administered to the rats. The lead isotope ratios were determined by inductively coupled plasma mass spectrometry (ICP-MS).
  
  
  RESULTS
  There are significant differences (p<0.05) in lead isotope ratios between blood, urine, and feces. Moreover, a nonlinear relationship between the blood lead concentration and the blood lead isotope ratios was observed. There is also a threshold effect to the fractionation function. Only the blood isotope ratio of (204)Pb/(206)Pb matches the test substance well. As for feces, when (204)Pb/(206)Pb ratio is considered, there is no significant difference between feces-test substance pairs in medium and high dose group.
  
  
  CONCLUSIONS
  The biological fractionation of lead isotopes in SD rats was observed. Moreover, there might be a threshold for the biological fractionation of lead isotopes which is depending on whole blood lead level. It is considered to be more reliable that we compared the isotope ratios of potential lead hazards with both blood and feces lead fingerprints especially for (204)Pb/(206)Pb ratio under high-dose exposure.
authors.affiliation: School of Public Health, Peking University, Haidian District, Beijing, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
authors.forename: Duojian
authors.initials: D
authors.lastname: Liu
authors.forename: Qing
authors.initials: Q
authors.lastname: Xie
authors.forename: Jingyu
authors.initials: J
authors.lastname: Wang
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000097:blood / Q000737:chemistry / Q000378:metabolism / Q000652:urine; D005243:Feces / Q000737:chemistry; D007554:Isotopes / Q000097:blood / Q000737:chemistry / Q000378:metabolism / Q000652:urine; D007854:Lead / Q000097:blood / Q000737:chemistry* / Q000378:metabolism* / Q000652:urine; D007855:Lead Poisoning / Q000097:blood / Q000378:metabolism* / Q000652:urine; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012137:Respiratory System / Q000187:drug effects*
chemical_list: D015415:Biomarkers; D007554:Isotopes; D007854:Lead