The Use of Biomarkers in Vertebrates

Abstract

In field studies biomarker assays can provide evidence of exposure of vertebrates to environmental chemicals, and sometimes also of consequent harmful effects. Appropriate combinations of assays can measure the sequence of changes which lead to the appearance of overt symptoms of toxicity; they can record changes at different organisational levels, ranging from the molecular, through the cellular, to effects upon the whole organism (physiological and behavioural). Assays that only require non destructive sampling have two major advantages, one scientific the other ethical. From the scientific viewpoint they can be based on serial sampling of individuals, thereby eliminating the problem of interindividual variations in the parameters that are measured. From the ethical point of view, there is growing opposition to testing procedures that cause suffering or death to vertebrate animals. Samples of blood, faeces or eggs can be taken without causing distress. Biomarker responses which are closely related to toxicity (eg those based upon the actual mechanism of toxicity) are of particular interest. They can give an integrated measure of the toxic effect of mixtures of compounds acting through the same mechanism (eg in the case of planar organohalogen compounds displaying Ah receptor - mediated toxicity), thus offering a way of approaching one of the most difficult problems in ecotoxicology. A major challenge is linking biomarker responses to consequent effects at the level of population and above. The success in linking eggshell thinning caused by DDE to the decline of certain raptor populations has demonstrated the potential of this approach. However much work needs to be done to make it more widely applicable. With the rapid advance of biochemical toxicology there is an excellent prospect for the development of new `user friendly’ assays to aid environmental risk assessment of vertebrates.