Tissue disposition and excretion of ¹⁴C-labelled aflatoxin B₁ after oral administration in channel catfish

The pharmacokinetics, tissue distribution and excretion of ¹⁴C-labelled aflatoxin B₁ (AFB₁) were examined after oral administration (250 μg/kg body weight) in channel catfish (Ictalurus punctatus). Plasma concentrations of parent AFB₁ were best described by a one-compartment pharmacokinetic model, in which peak plasma concentration (503 ppb) occurred at 4.1 hr after dosing. The absorption and elimination half-lives were 1.5 and 3.7 hr, respectively. AFB₁ was highly bound (95%) to plasma proteins. Concentrations of ¹⁴C (in AFB₁ equivalents) measured in the tissues were highest at 4 hr, ranging from 596 ppb in the plasma to 40 ppb in the muscle. AFB₁ residues were rapidly depleted; at 24 hr the concentrations in the plasma and muscle were 32 and <5 ppb, respectively. Concentrations in the bile exceeded 2000 ppb (at 24 hr), whereas the highest concentration in the urine was 51 ppb (4-6-hr collection interval). Renal and biliary excretion accounted for <5% of the administered dose, indicating incomplete absorption. Pharmacokinetic modelling and tissue data demonstrate a very low potential for the accumulation of AFB₁ and its metabolites in the edible flesh of channel catfish through the consumption of AFB₁-contaminated feed.