Uptake of benzo[a]pyrene, but not of phenanthrene, is inhibited by fatty acids in intestinal brush border membrane vesicles of rainbow trout (Oncorhynchus mykiss)

Abstract

Partial replacement of fish ingredients with vegetable ingredients has elevated levels of polycyclic aromatic hydrocarbons (PAHs) in Atlantic salmon reared on these feeds. PAH uptake in the intestinal tract is postulated to occur in association with lipid absorption and could well be affected by fatty acid composition. We therefore investigated the effects of a fish oil and vegetable oil fatty acid, eicosapentaenoic acid (EPA; 20:5n-3) and oleic acid (18:1n-9) respectively, on the uptake of benzo[a]pyrene (BaP) and phenanthrene (PHE) across the intestinal brush border membrane in the salmonid species rainbow trout (Oncorhynchus mykiss). BaP and PHE were solubilized in mixed micelles composed of either EPA or oleic acid and administrated to isolated brush border membrane vesicles (BBMV) derived from the pyloric caeca, proximal intestine and distal intestine. In the absence of free fatty acids (FFA) trans-membrane uptake of BaP and PHE was 2-7 times lower than the fraction associated to or in the membrane. In the presence of FFA, trans-membrane BaP uptake had decreased by 80 and 40% at the highest EPA and oleic acid concentration, respectively, whereas PHE uptake was virtually unaffected. In the presence of BaP, but not PHE, trans-membrane EPA uptake in BBMV had decreased. This study obtained evidence for PAH-dependent interactions with FFA uptake. We conclude that intestinal BaP uptake is reduced by luminal FFA contents whereas PHE uptake is not. A large fraction of the administrated BaP and PHE remains associated with the cellular membrane of enterocytes and may interfere with uptake of nutrients.

Keywords: Aquafeed; Eicosapentaenoic acid; Enterocyte; Intestinal uptake; Membrane partitioning; Oleic acid; Polycyclic aromatic hydrocarbons (PAHs); Trans-membrane uptake.