Aflatoxin B1 hepatic metabolism in four commercial poultry species

Abstract

Introduction. The adverse effects of aflatoxin B₁ (AFB₁) are caused by the metabolism of this mycotoxin, where toxic products as aflatoxin B₁ epoxide and aflatoxin B₁ dialdehyde are produced. Objective. The present study aims to determine the enzyme kinetic parameters of each metabolic stem in the AFB₁ metabolism pathway for the chicken, duck, quail and turkey and compare these parameters with in vivo AFB₁ effects. Materials and methods. Microsomal and cytosolic fractions were obtained by differential centrifugation and assayed in vitro. Incubations were performed under the appropriate conditions to determine the enzymatic parameters K_m, V_max and CL_int of the activities AFB1 epoxidase, aflatoxicol dehydrogenase, AFB₁ reductase, glutathione-S-transferase and AFB₁ aldehyde reductase. The detection of both the substrate and the biotransformation product was performed by high-performance liquid chromatography and the enzymatic parameters were determined by non-linear regression. Results. The duck presents the higher production of AFB₁ epoxide, which is associated with its high sensitivity. The ratio of aflatoxicol dehydrogenase to AFB₁ reductase activity is highest in ducks and lowest in chickens, indicating that AFB₁ has a greater cytosolic bioavailability for epoxidation in ducks, while glutathione transferase activity is higher in chicken breeds. Finally, the production of mono- and dialcohol aflatoxin B₁ is more efficient in chicken breeds and turkeys. Conclusions. Chicken resistance is due to greater efficiency of neutralization reactions and low rates of bioactivation and cytosolic bioavailability of AFB₁, in contrast to ducks, a highly sensitive species, or to species with intermediate sensitivity, such as turkeys and quails.