Chelated lead in relation to lead in bone and ALAD genotype.
In order to assess whether lead in bone is available for chelation by 2,3 meso-dimercaptosuccinic acid (DMSA), 21 workers (10 active and 11 retired) from a secondary lead smeltery were studied. A morning urine sample was obtained from all participants, followed by ingestion of 10 mg per kg body weight of the chelating agent DMSA. All urine produced during the following 24 h was collected in consecutive 6- and 18-h portions. Concentrations of lead in blood (B-Pb) and urine were determined by flameless atomic absorption spectrometry (AAS), in plasma (P-Pb) by inductively coupled plasma mass spectrometry (ICP-MS), and in finger bone (Bone-Pb) by K X-ray fluorescence technique (XRF). DMSA-chelatable lead excreted in the 24-h portion correlated well with the excretion in the 6-h portion (U-Pb6h; rs=0.95; P<0.001). U-Pb6h showed a non-linear relationship to B-Pb (rs=0.84; P<0.001) and linear relationships to P-Pb (rs=0. 91; P<0.001) and lead in morning urine (rs=0.95; P<0.001). In active workers, but not in retired ones, P-Pb and U-Pb6h showed some relationship to Bone-Pb. In alternative multiple regression models B-Pb or P-Pb were both significant predictors of U-Pb6h, while Bone-Pb did not significantly improve the models. It can, thus, be concluded that DMSA-chelatable lead mainly reflects lead concentrations in blood, soft tissues, and possibly also trabecular bone. It is not a good index of total body burden and long-term exposure. For such estimations cortical Bone-Pb is more valid, as it contains the major fraction of long-term accumulated lead in the body. Further, the mobilization test did not give better information than measurements of lead levels in blood, plasma, or urine without chelation.
D000367:Age Factors; D001822:Body Burden; D001842:Bone and Bones / Q000187:drug effects* / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D005385:Fingers; D005838:Genotype; D006801:Humans; D007854:Lead / Q000097:blood / Q000378:metabolism* / Q000652:urine; D013058:Mass Spectrometry; D008669:Metallurgy; D016273:Occupational Exposure; D000623:Porphobilinogen Synthase / Q000097:blood / Q000235:genetics*; D012044:Regression Analysis; D012179:Retirement; D013052:Spectrometry, X-Ray Emission; D013054:Spectrophotometry, Atomic; D004113:Succimer / Q000494:pharmacology* / Q000627:therapeutic use; D013997:Time Factors