Uptake and vascular transport of ingested aflatoxin.

The uptake and vascular transport of abomasally instilled aflatoxin B1 (AFB1) was investigated in sheep. Aflatoxin uptake was compared with that of palmitate, a water-insoluble oil known to be absorbed into the intestinal lymphatic drainage which bypasses the liver to enter the peripheral vascular circulation via the thoracic duct. After instillation into the abomasum, aflatoxin was detected in inferior vena cava blood within 30 min, while palmitate was not detected in vena cava blood at any time. Palmitate was detected in thoracic duct lymph after about 2 h. More than 95% of the palmitate in lymph was associated with the chylomicron fraction, while aflatoxin in either plasma or lymph was not detectably associated with any of the circulating lipoproteins. In addition, aflatoxin did not partition into plasma or lymph lipoproteins in vitro. Toxic lipophilic xenobiotics, such as benzo(a)pyrene and polychlorinated biphenyls (PCBs) do partition into lipoproteins, are absorbed into the intestinal lymphatic drainage, bypassing the liver to enter the peripheral vascular circulation directly, and are not specifically hepatotoxic. These data suggest that the mode of aflatoxin absorption from the gastrointestinal system results in its immediate transport to the liver, which may contribute to aflatoxin hepatotoxicity.