Immunological methods for dosimetry of heterocyclic amines

Biomarkers of exposure to heterocyclic amines: approaches to improve the exposure assessment

Various methods of exposure assessment, such as questionnaires, sometimes combined with pictures of cooked meat, have been employed in investigations on the relationship between heterocyclic amines (HA) and health effects. However, as the content of heterocyclic amines vary greatly with cooking conditions, it is difficult to obtain an accurate estimate of the exposure. To improve the exposure assessment, the use of biomarkers has been investigated. The metabolism of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is well characterised. In humans, the major part of the dose is excreted in urine within 24-48 h following a meal. A few percent is excreted as parent compounds, whereas the major part is metabolites. Urinary level of parent HA reflects only recent exposure. However, the pattern of excreted metabolites might indicate the capacity to activate or detoxify HAs. The excretion of glucuronide conjugates of N-hydroxy-PhIP and N-hydroxy-MeIQx could be a marker for the N-hydroxylation capacity and the dose of the proximate metabolites. Recently, we proposed 5-OH-PhIP as a marker for the ultimate reactive metabolite of PhIP, since it is formed from this compound as a by-product along with the formation of PhIP-DNA adducts. In a search for biomarkers reflecting exposure over some time, blood protein adducts with a longer lifespan have been investigated, and PhIP adducts of serum albumin and haemoglobin from meat-consuming humans were recently reported. Many compounds, like drugs, nicotine and narcotics, bind to melanin in hair and give information on exposure for longer time periods. In mice, PhIP is irreversibly incorporated in a dose-dependent manner into hair, and in humans exposed to an ordinary diet, it was found to vary from <50 to 5000 pg PhIP/g hair. The incorporation is also dependent on the content of eumelanin. The use of PhIP in hair as a biomarker of exposure is promising, but needs validation, using other methods of exposure assessment.

Methods for the determination of mutagenic heterocyclic amines and their applications in environmental analysis

The environmental analysis of heterocyclic amines is important to preserve human health, because all these compounds are potent mutagens and many are carcinogens in experimental animals. This review summarizes the analytical methods for the determination of mutagenic heterocyclic amines and their applications to various environmental samples. High-performance liquid chromatographic methods with ultraviolet, electrochemical and fluorescence detections are commonly used for the quantification of heterocyclic amines. Moreover, liquid chromatography-mass spectrometry, gas chromatography, gas chromatography-mass spectrometry, capillary zone electrophoresis and enzyme-linked immunosorbent assay are also developed. Heterocyclic amines in complex environmental matrices are present at low parts per billion or less, so that the sample preparation influences the reliable and accurate analysis of these compounds. Mutagenic heterocyclic amines are widely distributed in a number of ambient environmental components such as airbone particles, diesel-exhaust particles, cigarette smoke, cooking fumes, rain water, sewage water, incineration-ash and soil. These facts suggest that mutagenic heterocyclic amines are likely to be ubiquitous environmental pollutants and humans are continually exposed to these compounds in normal daily life.