The overall objective of this program of research is to conduct a thorough study of the absorption and metabolic activation in man of the major mutagens, MeIQx, DiMeIQx and PhIP, produced during the cooking of beef. Together, these compounds account for 60% of the mutagenicity of cooked meat. The results of these studies should help in the assessment of the relevance of these compounds to human cancer.
The specific aims are: 1. To measure the levels of MeIQx, and DiMeIQx in typical British and American diets to obtain estimates of the average daily intake (ADI) of these amines. The compound will be assayed using a highly specific and sensitive gas chromatographic-mass spectrometric GCMS method developed in this laboratory. 2. To assess the absorption of MeIQx and DiMeIQx from meat by measurement of the unchanged amines, or their major metabolites, in urine in human volunteers. In preliminary studies we have demonstrated that the GCMS assay developed for MeIQx is sufficiently sensitive for this purpose (see Progress Report). 3. To develop strategies to assess the degree of in vivo conversion of MeIQx and DiMeIQx to their reactive metabolites in man. A number of possible methods will be investigated, including the identification of a metastable metabolite of the reactive intermediate, and determination of adducts with haemoglobin or DNA. 4. To assess, by the methods to be developed above, the possible modifying influence of foods not containing MeIQx or DiMeIQx (e.g. high-fibre vegetables, vitamin c rich fruit, brassicaceous vegetables) on the absorption and/or activation of these amines. 5. To assess the body burden of MeIQx and DiMeIQx in volunteers eating typical British and American diets. 6. To determine in vivo, the extent to which the absorption and activation of MeIQx and DiMeIQx vary amongst individuals, and within an individual. To assess the effects of environmental factors such as cigarette smoking and alcohol consumption on the activation of the amines in vivo. 7. To develop a GCMS assay for PHIP in foods and body fluids and to apply this method in studies similar to those described above for MeIQx.
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