The teratogenic effects of E-64 on rat embryogenesis.

To examine the effects of E-64 (a thiol protease inhibitor) on the development of rat embryos, pregnant Wistar rats were injected with 10-30 mg/kg of E-64 intra-peritoneally on days 9 and 10 of gestation. On day 21, the rats were killed and the fetuses were examined for malformations. When 30 mg/kg of E-64 was administered, the incidence of resorptions and malformations was 25.7% and 60.4%, respectively. The most common malformations were hydrocephaly, exencephaly, anophthalmia, microphthalmia, hydronephrosis and renal hypoplasia. These results suggest that thiol protease inhibitor is teratogenic during early rat embryogenesis.