MEASUREMENT OF DNA-ADDUCTS IN HUMANS AFTER COMPLEX MIXTURE EXPOSURE

In contrast to acute or chronic dosing experiments with a single chemi cal in animals, man is exposed to thousands of chemicals during a life time. Each of these may act alone, additively, synergistically or anta gonistically in terms of biological effects, but most current risk ass essment procedures fail to recognize such interactions. In carcinogene sis, a mutational process that is thought to occur through DNA damage by endogenous and/or exogenous agents, a wide variety of host factors is involved in disease outcome. These include absorption of chemicals, their distribution, metabolism and excretion. In addition, once metab olic activation has occurred, there is an array of protective mechanis ms that cells have evolved to maintain DNA integrity, such as DNA repa ir, genetic redundancy and programmed cell death. One approach to risk assessment is to regard all DNA-damaging events as potentially leadin g to cancer and to measure DNA damage as the biologically relevant end point. The main method, if not the only method, presently available to assay a wide range of DNA adducts is P-32-postlabelling. This method has high sensitivity (limit of detection > 1 adduct per 10(10) nucleot ides) and is capable of visualizing many different DNA adducts in a si ngle analysis. Postlabelling is best suited for detecting hydrophobic adducts-low molecular weight adducts usually need a preliminary separa tion procedure prior to being postlabelled. This chromatographic proce dure has been used to study DNA samples from human tissues of cigarett e smokers, occupationally exposed groups and individuals living in pol luted environments. Correlations have been found between the severity of exposure and the level of DNA adducts detected for human samples. H owever, most studies are single-time point studies, whereas for risk a ssessment purposes it may be better to use more quantitative and repre sentative measures of long-term exposure, for example the number of ad ducts formed per annum. This article reviews methods of DNA adduct mea surement, with particular reference to the P-32-postlabelling techniqu e, which has been used to determine DNA adduct levels in populations e xposed to complex mixtures. Copyright (C) 1996 Published by Elsevier S cience Ltd