Protective effect of glutathione S-transferase enzyme activity against aflatoxin B 1 in poultry species: relationship between glutathione S-transferase enzyme kinetic parameters, and resistance to aflatoxin B 1

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 2.0 to 157.5 µM and the AFB -GSH produced was identified and quantitated by HPLC. Significant differences were found in GST V values, being the highest in chickens, followed by quail, ducks and turkeys. The K values were also significantly different, with chickens < ducks < turkeys < quail. Chickens had the higher CL value in contrast to ducks. Differences by sex showed that duck females had a higher CL value than the turkey and quail, whereas duck males had a CL close to that of turkey. The ratio "AFBO production /AFB -GSH production" follows the order duck>turkey>quail>chicken, in agreement with the known poultry sensitivity. The extremely high "AFB epoxidation activity/ GST activity" ratio observed in ducks might be the explanation for the development of hepatocellular carcinoma in this species.