Developmental Toxicity Studies of Triethylene Glycol Monomethyl Ether Administered Orally to Rats and Rabbits

Abstract

Triethylene glycol monomethyl ether (TGME) was administered orally via gavage stomach tube to mated Caesarean delivered (CD) rats and artificially inseminated New Zealand white rabbits on days 6–15 and 6–18 of gestation, respectively, at dose levels of 0, 625, 1,250, 2,500, or 5,000 mg/kg/day (rats) and 0, 250, 500, 1,000, or 1,500 mg/kg/day (rabbits). Clinical signs, maternal body weights, and feed consumption were monitored throughout the treatment period. The surviving rats and rabbits underwent Caesarean section on day 20 and day 29 of gestation, respectively. Fetuses were weighed, sexed, and examined externally and for soft tissue and skeletal alterations. In rats, the high dose significantly reduced maternal body weights, feed consumption, and gravid uterine weights. One dam in this group died on day 13 of gestation. Treatment-related clinical signs were seen only at the highest dose tested. Maternal feed consumption was significantly reduced at 5,000 and 2,500 mg/kg and slightly, but not significantly, reduced at 1,250 mg/kg. Doses as high as 5,000 mg/kg/day did not affect pregnancy rate, implantations, corpora lutea, live fetuses, or fetal sex ratios. Resorptions were significantly increased at 5,000 mg/kg, and fetal body weights were slightly reduced at 1,250 mg/kg and significantly reduced at 2,500 and 5,000 mg/kg. The incidences of malformations and external or internal soft tissue variations were not increased at doses as high as 5,000 mg/kg. Incidences of skeletal variations were increased at doses of 1,250 mg/kg and higher. The no-observable-effect level (NOEL) in rats, for both maternal and developmental toxicity, was 625 mg/kg, while 1,250 mg/kg was a no-observable-adverse-effect level (NOAEL) for maternal toxicity and may be very near the NOAEL for developmental toxicity. In rabbits, 1,500 mg/kg/day reduced maternal body weights and feed consumption and caused death, abortions, treatment-related clinical signs of toxicity, and reduced gravid uterine weights. One doe in the 1,000 mg/kg group died on day 18 of gestation, but no treatment-related signs were seen in the other animals in this group. Doses as high as 1,500 mg/kg did not significantly affect pregnancy rate, implantations, corpora lutea, resorptions, live fetuses, fetal body weights, or sex ratio. Incidences of malformations or external and internal variations were not increased at any of the dose levels. The only developmental toxicity seen in the rabbit was an increase in the incidence of two common skeletal variations, angulated hyoid alae and delayed ossification of the xiphoid process, at the highest dose tested. For maternal toxicity, the NOEL and NOAEL were 250 mg/kg and 500 mg/kg, respectively, and for developmental toxicity the NOEL and NOAEL were 1,000 mg/kg and 1,500 mg/kg, respectively. These studies indicate that TGME was not selectively toxic to developing rat or rabbit conceptuses.