Archives of Environmental Contamination and Toxicology

, Volume 44, Issue 1, pp 0116–0124

In Vitro Intestinal Lead Uptake and Transport in Relation to Speciation


  • A. G. Oomen
    • RITOX, Environmental Toxicology and Chemistry, Utrecht University, P.O. Box 80176, NL-3508 TD Utrecht, The Netherlands
  • J. Tolls
    • RITOX, Environmental Toxicology and Chemistry, Utrecht University, P.O. Box 80176, NL-3508 TD Utrecht, The Netherlands
  • A. J. A. M. Sips
    • National Institute of Public Health and the Environment, P.O. Box 1, NL-3720 BA Bilthoven, The Netherlands
  • J. P. Groten
    • TNO Nutrition and Food Research Institute, Toxicology Division, Utrechtseweg 48, NL-3700 AJ Zeist, The Netherlands

DOI: 10.1007/s00244-002-1226-z

Cite this article as:
Oomen, A., Tolls, J., Sips, A. et al. Arch. Environ. Contam. Toxicol. (2003) 44: 0116. doi:10.1007/s00244-002-1226-z


Children might be exposed substantially to contaminants such as lead via soil ingestion. In risk assessment of soil contaminants there is a need for information on oral bioavailability of soilborne lead. Oral bioavailability can be seen as the result of four steps: (1) soil ingestion; (2) mobilization from soil during digestion, i.e., bioaccessibility; (3) transport across the intestinal epithelium; and (4) first-pass effect. Lead bioaccessibility and speciation in artificial human small intestinal fluid, i.e., chyme, have been investigated in previous studies. In the present study, transport of bioaccessible lead across the intestinal epithelium was investigated using the Caco-2 cell line. Cell monolayers were exposed to (diluted) artificial chyme. In 24 h, approximately 27% of the lead were associated to the cells and 3% were transported across the cell monolayer, without signs of approaching equilibrium. Lead associated to the cells showed a linear relationship with the total amount of lead in the system. Bile levels did not affect the fraction of lead associated to Caco-2 cells. Extrapolation of the lead flux across the Caco-2 monolayer to the in vivo situation indicates that only a fraction of the bioaccessible lead is transported across the intestinal epithelium. Furthermore, the results indicate that as the free Pb2+ concentration in chyme was negligible, lead species other than the free metal ion must have contributed to the lead flux toward the cells. On the basis of lead speciation in chyme, this can be attributed to dissociation of labile lead species, such as lead phosphate and lead bile complexes, and subsequent transport of the released free metal ions toward the intestinal membrane.

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© Springer-Verlag New York Inc. 2003