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-1-8,9-epoxide (AFBO) with glutathione, and the relationship with aflatoxin B-1 (AFB(1)) 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-max), Michaelis-Menten constant (K-m) and intrinsic clearance (CLint) for GST activity. AFB(1) used ranged from 2.0 to 157.5 mu M and the AFB(1)-GSH produced was identified and quantitated by HPLC. Significant differences were found in GST V-max values, being the highest in chickens, followed by quail, ducks and turkeys. The K-m values were also significantly different, with chickens < ducks < turkeys < quail. Chickens had the higher CLmt value in contrast to ducks. Differences by sex showed that duck females had a higher CLmt value than the turkey and quail, whereas duck males had a CLmt close to that of turkey. The ratio "AFBO production/AFB(1)-GSH production" follows the order duck>turkey>quail>chicken, in agreement with the known poultry sensitivity. The extremely high "AFB(1) epoxidation activity/GST activity" ratio observed in ducks might be the explanation for the development of hepatocellular carcinoma in this species.