A modified Drosophila assay for screening developmental toxicants was described. The assay utilized Oregon-R wild type Drosophila- melanogaster. Flies were exposed to the test agent from the egg through three larval stages by incorporating five range finding concentrations of the chemical into the culture medium. A total of 200 emergent adult flies were examined intact and scored for a bent humeral bristle and a notch in the wing blade. After the data were analyzed by probit techniques, the concentrations of the test agent were adjusted to provide at least three challenge concentrations. The protocol was repeated using a minimum of 500 pooled flies per concentration over three runs. If statistically significant results were not obtained, additional trials using adjusted concentrations were performed. The modified assay was used to evaluate 18 compounds. Urethane (51796), meprobamate (57534), hydroxyurea (127071), vincristine-sulfate (2068782), procarbazine-hydrochloride (366701), 2,4,5-T (93765), caffeine (58082), acetazolamide (59665), EM-12 (26581817), 6-aminonicotineamide (329895), acetylsalicylic- acid (50782), ethanol (64175), and cyclophosphamide (50180) were known developmental toxicants. Sodium-saccharin (128449), formaldehyde (50000), diphenylhydramine-hydrochloride (147240), nitrilotriacetic-acid (139139), and amaranth (915673) were nondevelopmental toxicants. Among the developmental toxicants, all except ethanol, acetylsalicylic-acid, and cyclophosphamide gave positive responses in the modified assay. All nondevelopmental toxicants except sodium-saccharin were identified correctly. The responses indicated a sensitivity of the modified assay of 77%, a specificity of 80%, and overall accuracy of 78%. Experiments leading to optimization of the assay were described. The authors conclude that the modified assay using intact Drosophila can be used to screen chemicals for developmental toxicity.
Dennis W. Lynch, National Institute for Occupational Safety and Health (Mail Stop C-23), Robert A. Taft Laboratories, 4676 Columbia Parkway, Cincinnati, OH 45226-1998