Microsomal and cytosolic biotransformation of aflatoxin B1 in four poultry species

Abstract

1. This research evaluated differences in hepatic in vitro metabolism of aflatoxin B1 (AFB1) on selected avian species. 2. Microsomal and cytosolic liver fractions were obtained from chickens, ducks, quails and turkeys; eight males and eight females of each. 3. All microsomes studied produced AFB1-8,9-exo-epoxide (AFBO), a metabolite regarded as the active product of AFB1. Turkey microsomes produced 1.8 and 3.5 times more AFBO than quails and chickens microsomes, respectively. 4. Males from evaluated birds produced more AFBO than females, but statistically-significant differences between genders were observed only in ducks and turkeys. 5. The cytosolic fraction from all four species produced aflatoxicol (AFL). Turkey and duck hepatic cytosol produced more AFL than from quail and chickens. 6. It is known that turkeys are very sensitive to AFB1, quails are intermediate and chickens are particularly resistant; the differences in AFBO production shown in our study may help to explain the difference in vivo responses among turkeys, quail and chickens. 7. Moreover, AFL may be related to AFB1 toxicity; it was produced in larger amounts by hepatic cytosol from the more susceptible species. 8. Because AFBO production by microsomes in ducks was relatively low, it is possible that other toxicity mechanisms are involved in this highly susceptible species.

The role of selected cytochrome P450 enzymes on the bioactivation of aflatoxin B1 by duck liver microsomes

“…The compounds were separated using a linear gradient of A (waterÁ0.1% formic acid) and B (methanolÁ0.1% formic acid) as follows: 0 min, 30% B; 2 min, 30% B; 7 min, 55% B; and 7.01 min, 30% B. The two analytes were monitored by fluorescence detection at excitation and emission wavelengths of 365 nm and 425 nm, respectively (Gallagher et al, 1996;Lozano & Diaz, 2006). A 1:100 dilution was made, from which 2 ml was injected into the chromatograph.…”

“…AFB1 and AFBO determination was carried out at 408C, at a flow rate of 0.35 ml/min. The AFBO production was monitored as the AFB1Ádhd adduct, which was quantitated using AFB2a as standard (given the similar spectral properties of AFB1-dhd and AFB2a), as described by Lozano & Diaz (2006). The compounds were separated using a linear gradient of A (waterÁ0.1% formic acid) and B (methanolÁ0.1% formic acid) as follows: 0 min, 30% B; 2 min, 30% B; 7 min, 55% B; and 7.01 min, 30% B.…”

“…Although the AFB1 bioactivation to AFBO is relatively well understood in mammals, studies in poultry are still needed. We previously reported differences in the rate of biotransformation of AFB1 into the epoxide form in commercial poultry species including ducks, chickens, turkeys and quails (Lozano & Diaz, 2006). The highly sensitive duck produced twice as much AFBO compared with the less sensitive chicken.…”

Enzymatic activity in turkey, duck, quail and chicken liver microsomes against four human cytochrome P450 prototype substrates and aflatoxin B1

“…These results also confirm that the differences in sensitivity to AFB1 among poultry species can be partially explained by differences in the relative enzymatic properties of the CYP avian orthologs responsible for AFB1 bioactivation. 35 This study also shows that the turkey liver microsomes are the most efficient bioactivating AFB1 to AFBO, followed by quail, duck and chicken enzymes. In order to completely understand how AFB1 is biotransformed in avian species and how metabolism determines in vivo sensitivity it is necessary to further investigate phase I and specially phase II metabolism of AFB1 in poultry.…”

Biotransformation of Aflatoxin B1 and Its Relationship with the Differential Toxicological Response to Aflatoxin in Commercial Poultry Species

“…This reaction is not catalyzed by microsomal enzymes but by a cytosolic NADPH-dependent enzyme that in the case of the chicken has an estimated molecular weight of 46.5 KDa and is inhibited by the 17-ketosteroids androsterone, dehydroisoandrosterone and estrone (Chen et al, 1981). Formation of AFL was first reported in chicken, duck, turkey and rabbit liver cytosol (Patterson & Roberts, 1971), and it also occurs in quail (Lozano & Diaz, 2006). However, little or no activity has been observed in guinea pig, mouse or rat liver cytosol (Patterson & Roberts, 1971).…”