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 2.0 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.