TERATOGENESIS ASSOCIATED WITH OXYDEMETON-METHYL IN THE STAGE-12 CHICK-EMBRYO

The teratogenic potential of oxydemeton-methyl (ODM) was investigated using a stage specific localized topical method of application to the stage 12 chick embryo. A dose of 0.01, 0.05, 0.10, 0.50, 1.0, or 2.0 m g/embryo was applied to the vitelline membrane directly above the stag e 12 embryo. The embryo was then returned to the incubator and monitor ed daily until stage 41 (15 day). At stage 41 the embryo was autopsied and examined for gross external and internal malformations, wet weigh t, and crown-rump length. Experimental data was compared to unopened a nd saline treated controls. At doses less than 0.50 mg/embryo, surviva l rates were high (>80%) but when that dose was exceeded, the survival rate fell significantly (P<0.001). A dose-dependent increase in malfo rmation rate was seen in all treatment groups with 0.10 mg/embryo, pro ducing a maximum malformation rate (19/33) with minimum mortality (3/3 6). Crown-rump lengths and wet weights were significantly less than co ntrols in all treatment groups (P<0.001). Anomalies were primarily see n in the musculoskeletal (ventral midline, limb, and neck) and cardiov ascular (ventricular septum and aortic arches) systems. Thoracogastros chisis and ventricular septal defects were the most common combination of malformations. Our data suggest that ODM is teratogenic when topic ally applied to the stage 12 chick embryo. (C) 1993 Wiley-Liss, Inc.