A novel nonmetric multivariate approach to the evaluation of biomarkers in terrestrial field studies

Abstract

This study evaluated the usefulness of using groups of biomarkers as measures of exposure and which statistical approach wouldbe most robust for analysing such data. We used both analysis of variance (ANOVA) and nonmetric cluster and associationanalysis (NCAA) to look for patterns in biomarker responses of populations of gray-tailed voles (Microtus canicaudus)in field enclosures exposed to azinphos-methyl (Guthion2S) at 0.0, 1.55 and 4.67 kg active ingredient(AI)ha-1 (four enclosures per treatment level). Biomarkers measured were hematocrit,total leukocyte counts, leukocyte differentiation, plasma lactate dehydrogenase (LDH), isocitratedehydrogenase, creatine phosphokinase (CPK) activities, and plasma creatinine and blood urea nitrogenconcentrations. Brain cholinesterase (AChE) activity was measured in a subset of animals. The ANOVAwas able to distinguish differences between treatment groups only for brain AChE. The NCAA confirmedthe ANOVA analysis that brain AChE activity differed significantly among the treatment groups. However,NCAA also identified LDH and CPK activity, and neutrophil and lymphocyte numbers as importantdiscriminants of pesticide treatment. Additionally, changes in blood cell parameters due to spatialgradients were layered over the effects due to the pesticide.