Immunological methods for dosimetry of heterocyclic amines

Carcinogenic heterocyclic amines are formed by common household cooking procedures, and it is therefore of interest to evaluate exposures in the general population. High-affinity monoclonal antibodies to 2-amino-l-methyl-6-phenyl- imidazo[4,5-b]pyridine (PhIP1) were produced and a sensitive fluorescence-based ELISA assay developed with a 50% inhibition by 150 fmoles PhIP or PhlP- metabolites modified in the 2-position. PhIP antigenic material was excreted mainly from 0-24 hours after a single meal containing fried meat in two volunteers and dropped to background levels after 48 hours. Urine samples (24 hours) were collected from 265 Danish males and females aged 40-70 years. The participants were also asked to fill in a questionnaire regarding their recent intake of fried and otherwise cooked meat. Excretion of PhlP-antigenic material was observed among those who had been eating Med meat with a median excretion of 1.5μg/24 hours. A higher median excretion among all samples of about 2.3μg/24 hours was observed when acid hydrolyzed samples were analyzed. This indicates that a large proportion of conjugated metabolites are present before hydrolysis, since these metabolites are not as efficient competitors for the antibody in ELISA. The excretion of PhIP antigenic materials showed a skewed normal distribution. These observations are close to predicted exposure rates in the general population, based on food consumption figures and analyses of PhIP in fried meat samples. PhIP antigenic material was always found to be present in urine samples from individuals who reported a recent intake of fried meat. Positive samples were also found among individuals who reported no recent intakes of fried or browned meat. The possible sources of this exposure are discussed.