Intestinal absorption of ¹⁴C from ¹⁴C-phenanthrene, ¹⁴C-benzo[a]pyrene and ¹⁴C-tetrachlorodibenzo-para-dioxin: approaches with the Caco-2 cell line and with portal absorption measurements in growing pigs

Abstract

-The aim of this work was to study the transfer through the intestinal barrier of two polycyclic aromatic hydrocarbons (PAHs) (benzo[a]pyrene and phenanthrene) and a dioxin (2,3,7,8-tetrachlorodibenzo-para-dioxin) which differed in their physicochemical properties. Both in vitro and in vivo assays were performed. For the in vitro study, Caco-2 cells, cultivated on permeable filters, permitted to measure the transepithelial permeability of the studied 14 C-labelled molecules. For the in vivo study, portal absorption kinetics were evaluated in pigs fed contamined milk. The results showed that all the molecules were absorbed and demonstrated a differential intestinal absorption for the studied molecules. Phenanthrene appeared to be the fastest and most uptaken compound, followed by benzo[a]pyrene and finally 2,3,7,8-tetrachlorodibenzo-para-dioxin. Their absorption levels were respectively 9.5, 5.2 and 1.4% after a 6 h-exposure in vitro and 86.1, 30.5 and 8.3% in vivo for the 24 h following ingestion. These findings suggest that the physicochemical properties of the xenobiotics and intestinal epithelium play key roles in the selective permeability and in the bioavailability of the tested micropollutants.

Influence of dietary fat type on benzo(a)pyrene [B(a)P] biotransformation in a B(a)P-induced mouse model of colon cancer

“…Using the Caco-2 cell model, Vasiluk et al [65] have demonstrated that uptake of B(a)P released into the gut lumen occurs through passive diffusion and its transfer into the bloodstream is aided by the fugacity gradient generated by the lipids. Additionally, works of Laurent et al [66,67] and Cavret et al [68] have shown a robust relationship between B(a)P and phenanthrene absorption and fat absorption. These studies reinforce the likelihood that prolonged exposure to B(a)P through dietary fat contributes to increased bioavailability of B(a)P and/or its metabolites in the GI tract and cause localized damage to the colon epithelium.…”

Polycyclic Aromatic Hydrocarbons in Food - Scientific Opinion of the Panel on Contaminants in the Food Chain

“…In 40 kg castrated pigs fed milk containing radiolabelled benzo[a]pyrene or phenanthrene (235 and 49 µg/L, respectively, corresponding to approximately 5.9 and 1.2 µg/kg b.w.). Cavret et al (2003) found absorption rates of 30.5% and 86.1%, respectively.…”

Bioavailability and Risk Assessment of Orally Ingested Polycyclic Aromatic Hydrocarbons

“…These results indicate that absorption of the four- and five-membered ring compounds (DMBA and B[a]P) was strongly dependent on the presence of bile in the intestinal lumen. Studies of Cavret et al (2003) provide further evidence that physicochemical properties of PAHs play a key role in intestinal permeability and bioavailability. The absorption of phenanthrene and B[a]P respectively were 9.5 and 5.2% after a 6-h exposure in Caco-2 cells, and 86.1% and 30.5%, respectively, 24 h following ingestion in pigs.…”