To further characterize the Drosophila-based prescreen to detect developmental toxicants, triethylene glycol (TEG), triethylene glycol monomethyl ether (TEGMME) and triethylene glycol dimethyl ether (TEGDME) were evaluated using our published protocol (Teratogenesis, Carcinogenesis, and Mutagenesis 11:147-173, 1991). One or two experiments, each employing 10 equimolar concentrations (.0013-1.64mM/vial) of test chemical and including a concurrent control, were conducted per chemical. Drosophila were exposed throughout development (egg through third instar larva) in culture vials to medium containing the test chemical. Each vial contained 1g of powdered medium and 5ml of distilled deionized water or a solution of test chemical in water. A mated, untreated, Oregon-R wild-type female (Mid-American Drosophila Stock Center, BGSU, Ohio) was added to each culture vial and allowed to oviposit for 20 hours, then removed. Emerging offspring were collected over 10 days and examined microscopically (25x) for bent humeral bristles-a morphological defect shown to occur with an increased incidence in fruit flies exposed to developmental toxicants. The incidence of bent bristles was statistically increased compared to concurrent controls (chi-square) at the two highest TEG concentrations - 1.32mM, 38/181, p<0.001 and 1.64mM, 29/99, p<0.001. For TEGMME, the incidence of bent bristles was statistically increased at the four highest concentrations - 0.66mM, 8/155, p<0.01; 0.99mM, 12/134, p<0.001; 1.32mM, 11/75, p<0.001; and 1.64mM, 3/5, p<0.001. For TEGDME, the incidence of bent bristles was statistically increased at three concentrations - 0.34mM, 10/159, p<0.01; 0.66mM, 28/171, p<0.001; and 0.99mM, 6/25, p<0.001) - no flies emerged at 1.32 and 1.64mM. Based on these results, TEGDME > TEGMME > TEG in terms of developmental toxicity. Results with TEG, TEGMME and TEGDME parallel the developmental toxicity seen in mammals and support further utilization of this Drosophila-based assay as a prescreen for developmental toxicants.
The Toxicologist. Society of Toxicology 43nd Annual Meeting and ToxExpo, March 21-25, 2004, Baltimore, Maryland