approximation to aflatoxin B metabolism and sensitivity in commercial poultry species based on empirical mathematical equations.

Enzyme kinetic parameters for aflatoxin B metabolism have been reported for chicken, quail, turkey and duck, but an integrated model has not been proposed. Both enzyme-catalyzed reactions and spontaneous reactions were modeled in the CellDesigner software and results were adjusted to Hill, Rational and Hoerl models. Results revealed that the higher amount of aflatoxin B epoxide produced in a short lapse of time and a low production of epoxide conjugated to glutathione explains the severe genotoxic effect of aflatoxin B in duck.

Protective effect of glutathione S-transferase enzyme activity against aflatoxin B in poultry species: relationship between glutathione S-transferase enzyme kinetic parameters, and resistance to aflatoxin B.

Comparative studies designed to investigate the role of glutathione S-transferase (GST) activity on the enzyme catalyzed trapping of aflatoxin B-8,9-epoxide (AFBO) with glutathione, and the relationship with aflatoxin B (AFB) resistance have not been conducted in poultry. Hepatic cytosolic fractions of chickens, quail, turkeys and ducks were used to measure in vitro the enzymatic parameters maximal velocity (V), Michaelis-Menten constant (K) and intrinsic clearance (CL) for GST activity. AFB used ranged from 2.

In vitro hepatic aflatoxicol production is related to a higher resistance to aflatoxin B in poultry.

A study was conducted to determine the cytosolic in vitro hepatic enzymatic kinetic parameters V, K, and intrinsic clearance (CL) for aflatoxin B (AFB) reductase [aflatoxicol (AFL) production] and AFL dehydrogenase (AFB production) in four commercial poultry species (chicken, quail, turkey and duck). Large differences were found in AFB reductase activity, being the chicken the most efficient producer of AFL (highest CL value). Oxidation of AFL to AFB showed only slight differences among the different poultry species.

An unusually high production of hepatic aflatoxin B-dihydrodiol, the possible explanation for the high susceptibility of ducks to aflatoxin B.

A study was conducted to determine the enzymatic kinetic parameters V, K, and intrinsic clearance (CL) for the hepatic in vitro production of aflatoxin B-dihydrodiol (AFB-dhd) from aflatoxin B (AFB) in four commercial poultry species, ranging in sensitivity to AFB from highest (ducks) to lowest (chickens). Significant but small differences were seen for V, while large significant differences were observed for K. However, the largest inter-species differences were observed for the CL parameter, with ducks being extraordinarily efficient in converting AFB into AFB-dhd.

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

A study was conducted to determine the cytochrome (CYP) P450 enzymes responsible for the bioactivation of aflatoxin B1 (AFB1) into its epoxide form (AFBO) in duck liver microsomes. Six male and six female 6-week-old Pekin ducks were used. The biochemical toxicology strategies applied included the use of selective inhibitors, prototype substrate activity for specific human P450s, correlation between aflatoxin bioactivation and enzymatic activity of prototype substrates, and the expression of specific CYP450 enzymes using antibodies against human CYP450s.