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 (CL(int)) for GST activity. AFB(1) used ranged from 2.0 to 157.5 µM 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 CL(int) value in contrast to ducks. Differences by sex showed that duck females had a higher CL(int) value than the turkey and quail, whereas duck males had a CL(int) 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.