In vitro evidence of the influence of complexation of Pu and Am on uptake by human lung epithelial cells Calu-3

Understanding the mechanisms involved in retention and clearance of actinides from the lungs after accidental intake is essential for the evaluation of the associated radiological risks. Although the absorption of radioelements has been shown in vivo to depend on their nature and physico-chemical properties, their mechanisms of translocation remain unknown. In this study, we have evaluated in vitro the binding and uptake by bronchial epithelial cells Calu-3 of 2 transuranic actinides, plutonium (Pu) and americium (Am), as the first steps of translocation across the pulmonary barrier. For this purpose, Calu-3 cells grown to confluence in 24-well plates were exposed to the radioelements for 24 h under various culture conditions. Two compartments were identified for the association of actinides to cells, corresponding to the membrane bound and internalized fractions. Binding of Pu was slightly higher than of Am, and depended on its initial chemical form (nitrate, citrate, colloids). Uptake of Pu and Am nitrate was higher in serum-free conditions than in supplemented medium, with an active mechanism involved in Pu internalization. Overall, our results suggest that complexation of actinides to bioligands may have an influence on their uptake by pulmonary epithelial cells, and therefore possibly on their subsequent absorption into blood. [Display omitted] •The membrane bound and internalized fractions of actinides are 2 differentially regulated compartments.•Actinide binding to cell membranes depends on nature (Pu, Am) and initial chemical form (nitrate, citrate, colloids).•Complexation of actinides with serum bioligands or DTPA inhibits their binding and uptake by cells.•Uptake of Pu nitrate is higher in serum-free conditions than in the presence of serum, and involves an active mechanism.•Internalization of Pu in the presence of serum is passive, as well as of Am whatever the incubation conditions.