Biochemical Factors Underlying the Age-Related Sensitivity of Turkeys to Aflatoxin B1
Comparative Biochemistry and Physiology - Part C: Toxicology and Pharmacology
Poultry are some of the most sensitive species to the toxic effects of aflatoxin B1 (AFB1), and younger poultry are more sensitive to this mycotoxin. To elucidate the mechanisms for this age-related susceptibility, various enzyme activities relevant to AFB1 were measured in liver microsomes prepared from male turkeys 9, 41 and 65 days of age. Hepatic microsomal o-dealkylation of methoxy- and pentoxyresorufin significantly increased, while that of ethoxyresorufin decreased with age. Microsomal AFB1 activation to the reactive AFB1-8,9-epoxide (AFBO) was most efficient in the youngest birds, with apparent Km and Vmax values of 168 and 19, 110 and 6, and 116 μM and 10 nmol/mg/min for 9, 41 and 65-day-old birds, respectivelly. The activity of hepatic cytosolic glutathione S-transferases (GSTs) was deficient in the youngest age group, but were higher in the older groups. There was also an age-related increase in the expression of GST isoforms Yc, Yc2, as well as AFB1-aldehyde reductase (AFAR). However, livers from all ages lacked specific GST-mediated conjugation of AFBO, indicating that turkeys are deficient in this key AFB1-detoxification pathway. Our data indicate that efficient activation may underlie the extreme sensitivity of young turkeys to the toxic effects of AFB1.
Klein, P.J., Van Vleet, T.R., Hall, J.O. and R. A. Coulombe, Jr. (2002). Biochemical factors underlying the age-related sensitivity of turkeys to aflatoxin B1. Comparative Biochemistry and Physiology 132, 193-201.