Relative potency of four ethylene glycol ethers for induction of paw malformations in the CD-1 mouse.

Time-mated CD-1 mice were orally dosed on gestation day 11 (plug = 0) with distilled water (control) or one of four glycol ethers at a dose of 4 mmol/kg: ethylene glycol monomethyl ether (EGME, 304 mg/kg), ethylene glycol dimethyl ether (EGdiME, 361 mg/kg), diethylene glycol dimethyl ether (diEGdiME, 537 mg/kg), triethylene glycol dimethyl ether (triEGdiME, 713 mg/kg). Fetuses were collected on gestation day 18, weighed, and examined for gross external malformations. Fetuses were cleared and stained to examine paws. There were no signs of treatment-related maternal toxicity, and intrauterine survival was unaffected by glycol ether treatments. Fetal body weights were significantly reduced only in litters treated with EGdiME. There was no treatment-related pattern of gross external malformations other than paw defects. Only triEGdiME failed to produce a significant incidence of malformations. Paw defects were present in 87.5% of EGME-treated litters (68.5% of fetuses), 86.7% of EGdiME-treated litters (33.8% of fetuses), and 77.8% of diEGdiME-treated litters (39.7% of fetuses). Hindpaw defects predominated over forepaw, and syndactyly was the most common malformation. The incidences of oligodactyly and short digits were also significantly increased. The similarity of malformations produced by these methyl-substituted glycol ethers is proposed to be attributable to in vivo conversion to a common teratogen, methoxyacetic acid.