Abstract
Aflatoxin B1 aldehyde reductase (AFAR) enzyme activity has been associated to a higher resistance to the aflatoxin B1 (AFB1) toxicity in ethoxyquin-fed rats. However, no studies about AFAR activity and its relationship with tolerance to AFB1 have been conducted in poultry. To determine the role of AFAR in poultry tolerance, the hepatic in vitro enzymatic activity of AFAR was investigated in liver cytosol from four commercial poultry species (chicken, quail, turkey and duck). Specifically, the kinetic parameters Vmax, Km and intrinsic clearance (CLint) were determined for AFB1 dialdehyde reductase (AFB1-monoalcohol production) and AFB1 monoalcohol reductase (AFB1-dialcohol production). In all cases, AFB1 monoalcohol reductase activity saturated at the highest aflatoxin B1 dialdehyde concentration tested (66.4 μM), whereas AFB1 dialdehyde reductase did not. Both activities were highly and significantly correlated and therefore are most likely catalyzed by the same AFAR enzyme. However, it appears that production of the AFB1 monoalcohol is favored over the AFB1 dialcohol. The production of alcohols from aflatoxin dialdehyde showed the highest enzymatic efficiency (highest CLint value) in chickens, a species resistant to AFB1; however, it was also high in the turkey, a species with intermediate sensitivity; further, CLint values were lowest in another tolerant species (quail) and in the most sensitive poultry species (the duck). These results suggest that AFAR activity is related to resistance to the acute toxic effects of AFB1 only in chickens and ducks. Genetic selection of ducks for high AFAR activity could be a means to control aflatoxin sensitivity in this poultry species.
Highlights
Aflatoxin B1 (AFB1) is a secondary metabolite produced by some strains of Aspergillus fungi, including Aspergillus flavus, A. parasiticus, A. nomius and A. pseudonomius
The molecular mass of the chemically-synthetized AFB1 monoalcohol was confirmed by mass spectrometry, since the peak eluting at tR = 13.92 minutes (Fig 2A) had the expected protonated monoisotopic mass of the compound (349.2 Da; Fig 2B)
The molecular mass of the AFB1 dialcohol was confirmed, given that the mass of the peak eluting at tR = 12.29 minutes (Fig 3A) corresponded to the expected protonated monoisotopic mass (351.0 Da; Fig 3B)
Summary
Glucose 6-phosphate sodium salt, glucose 6-phosphate dehydrogenase, nicotinamide dinucleotide phosphate (NADP+), ethylenediaminetetraacetic acid (EDTA), bicinchoninic acid solution (sodium carbonate, sodium tartrate, sodium bicarbonate and sodium hydroxide 0.1 N pH 11.25), copper sulphate pentahydrate, formic acid, sucrose, bovine serum albumin, sodium borohydride, m-chloroperbenzoic acid, ethanol (spectrophotometric grade), isopropyl alcohol, 2-(cyclohexylamino) ethane sulfonic acid (CHES), aflatoxin B2a and N,N-dimethylformamide were from Sigma-Aldrich (St. Louis, MO, USA). Sodium phosphate dibasic anhydrous and sodium chloride were from Merck (Darmstadt, Germany). Acetonitrile and water were all HPLC grade
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