PARENT SESSION

1D - Soil and Sediment Contamination
Poster Hall
8:30 AM - Tuesday, 29 April 2003
Chair: Van Noort, P.¹, ¹
Co-chair: Gerhardt, A.², Gerhardt, A.², ²

(TUP/7) Bioavailability of heavy metals absorption in human intestinal Caco-2 cells.

Yamada, Aya¹, Ono, Yoshiro¹, Sakai, Yasuyuki², ¹ Faculty of Environmental Sciences and Technology, University of Okayama, Okayama, Okayama, Japan² Institute of Industrial Science, University of Tokyo, Tokyo, Tokyo, Japan

ABSTRACT- A toxicity of ingested heavy metals depends largely on its bioavailability. Leaching characteristics and absorption ratios of influence bioavailability of heavy metals and it has been suggested that simple bioavailability-predictive extraction tests cannot estimate absolute bioavailability. A more accurate bioavailability-predictive test should be conducted. Therefore, we investigated the absorption ratios of heavy metals through human intestinal cell culture model Caco-2 cells. They have been used to study uptake and transport of several metals. A sample soil was collected from a landfill site of waste disposal, where slag, plastic, sludge were disposed of about 4 years ago. Cadmium, lead, and chromium contents of the sample are 18.2, 1074, and 3797 mg/kg, respectively. First, we investigated dissolved concentrations of heavy metals in the model stomach and stomach + small intestine solution by bioavailability-predictive extraction test. This result suggests that levels of dissolved cadmium, lead, and chromium in the model stomach solution were higher than those found in its stomach + small intestine counterpart. Heavy metals dissolved in the model stomach solution had a pH level of 2.0, while they decreased in the small intestine upon titration from a pH level of 2.0 to 7.0. A ratio of released amounts versus contents in the model stomach + small intestine was less than 50%. Second, Caco-2 cells were cultivated on from apical side and exposed to various liquid-to-solid ratio extractions of the sample in the model stomach + small intestine solution. High osmotic pressure with potassium and calcium significantly prevented cell proliferating in low liquid-to-solid ratio extraction. The cells could transport chromium to basal side across monolayer. This result suggests that chromium might be absorbed in small intestine. Heavy metals concentrations in the extractions and the media were determined by ICP-OES.

Key words: heavy metals , bioavailability, Caco-2 cells