Quantification and validation of enzyme immunoassay for urinary aflatoxin B-1-N-7-guanine adduct for biological monitoring of aflatoxins

The aflatoxin B-1-N-7-guanine (AFB(1)-N-7-guanine) adduct has been establis hed as one of the relevant biomarkers of dietary aflatoxin (AFB(1)) exposur e. Measurement of this adduct is potentially a useful dosimeter in molecula r epidemiological studies. This paper reports the application and evaluatio n of a sensitive indirect competitive enzyme-linked immunosorbent assay (EL ISA) for the detection and quantification of urinary AFB(1)-N-7-guanine add uct in high risk populations exposed to dietary aflatoxin. Earlier, we had reported a simple and rapid indirect ELISA method for AFB(1)-N-7-guanine ad duct in the urine and liver tissues using polyclonal antibodies specific to AFB(1)-N-7-guanine adduct. The method was evaluated using a rodent model ( Fischer 344), exposed to 1 mg kg(-1) body mass of AFB(1) and human urine sa mples obtained from a maize eating population, environmentally exposed to A FB(1) through their diet. The levels of AFB(1)-N-7-guanine adduct in rat an d human urine ranged from 6.42 to 20.16 mug mg(-1) creatinine and from 9.30 to 13.43 ng mg(-1) creatinine, respectively. The level of AFB(1) in the di et as estimated by ELISA ranged from 1000 to 3600 ng d(-1). The interesting observation in these studies is that the females (in both rodents and huma n subjects) are more efficient than males at excreting the adduct. Total ad duct (DNA bound adduct and guanine adduct excreted in urine) was found to b e similar in male and female rats. However, 63% of the total adduct was acc ounted for in urine of female rats, whereas male rats excreted 47% of the t otal adduct in their urine. The present method may find wide application as a biochemical tool in molecular epidemiological studies with respect to hu man exposure to dietary aflatoxins.