De kippe-embryotest. Fase I. Methodeontwikkeling voor onderzoek aan dioxines en furanan

Abstract

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Chicken embryos were used to develop an experimental bioassay to investigate the Toxicological Equivalency Factors (TEF) of dioxines and furans, and mixtures using the TEF principle for risk assessment of dioxins related compunds in reference to the public health. The animals were exposed to the chemicals by a single injection in the air sac of the egg. After incubation, liver microsomes were isolated from the chicken-embryo, in which activity of ethoxyresorufine-o-dealkylase (EROD), and the amount of cytochrome P-450 and protein were determined. The objective of the first phase, reported here, was to optimize the amount of vehicle, the method of isolation, the time of injection and the duration of incubation and exposure. The best suitable vehicle appeared to be 25 mul dioxane, mixed with 25 mul of an isotonic salt solution per egg. Isolation of microsomes by ultracentrifugation turned out to be the mostly effective isolated method, compared to gelfiltration. Injection at the 17th day of incubation and an exposure time of 24 hours, prior to dissection, resulted in the highest EROD induction. The ED50 for EROD induction by 2, 3, 7, 8- tetrachlorodibenzodioxin determined was 10.8 ng/egg. In a second experiment the result was 9.2 ng/egg. For 2,3,4,7,8-pentachlorodibenzofuran the ED50 was assigned to 8.7 ng/egg.