Portal absorption of ¹⁴C after ingestion of spiked milk with ¹⁴C-phenanthrene, ¹⁴C-benzo[a]pyrene or ¹⁴C-TCDD in growing pigs

Polycyclic aromatic hydrocarbons (PAHs) and dioxins are lipophilic organic pollutants occurring widely in the terrestrial environment. In order to study the PAHs and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) transfer in the food chain, pigs have been fed with milk mixed either with ¹⁴C-phenanthrene, with ¹⁴C-benzo[a]pyrene or with ¹⁴C-TCDD. The analysis of portal and arterial blood radioactivity showed that both PAHs and TCDD were absorbed with a maximum concentration at 4-6 h after milk ingestion. Then, the blood radioactivity decreased to reach background levels 24 h after milk ingestion. Furthermore, the portal and arterial blood radioactivities were higher for phenanthrene (even if the injected load was the lowest) than these of benzo[a]pyrene or these of TCDD, in agreement with their lipophilicity and water solubility difference. Main ¹⁴C absorption occurred during the 1-3 h time period after ingestion for ¹⁴C-phenanthrene and during the 3-6 h time period for ¹⁴C-benzo[a]pyrene and for ¹⁴C-TCDD. ¹⁴C portal absorption rate was high for ¹⁴C-phenanthrene (95%), it was close to 33% for ¹⁴C-benzo[a]pyrene and very low for ¹⁴C- TCDD (9%). These results indicate that the three studied molecules have a quite different behaviour during digestion and absorption. Phenanthrene is greatly absorbed and its absorption occurs via the blood system, whereas benzo[a]pyrene and TCDD are partly and weakly absorbed respectively. However these two molecules are mainly absorbed via the portal vein.