English Abstract In order to evaluate the risk of samples contaminated
with mixtures polychlorinated dibenzo-p-dioxins, polychlorinated
dibenzofurans and planar biphenyls a chicken embryo bioassay is in
development at our Institute. In this bioassay the toxic potency of these
compounds is determined by means of the ethoxyresorufin-deethylation (EROD)
activity in the microsomal fraction of the chicken embryo liver. The
experiments showed a large variation between the basal EROD activities, and
the maximal induced EROD activities. The slope for most dose curves was
similar. The relative toxicity factors in the chick embryo test determined,
were compared to the international (i)-TEFs. The EROD induction by the
tetra- and penta-dioxins and -furans showed higher TEF in the chicken embryo
compared to the (i)-TEF, and the hexa- and heptachlorinated congeners are
undervalued in the chicken embryo assay. Then the chicken embryo assay was
used to evaluate the additive aspect of the TEF principle. The results
showed that additivity of the congeners was responsible for the EROD
induction at a low dose.
