Ototoxicity or teratogenicity. An analysis of drug-induced effects on the early development of the mammalian otocyst.

The 13th gestational day inner ear (otocyst stage) is particularly vulnerable to toxic influence from the environment during its further development. Ethacrynic acid in a concentration of 1 and 10 micrograms/ml caused complete arrest in development, and this was not overcome when withdrawing the drug after in vitro exposure to ethacrynic acid during 3 days. Gentamicin exposure at 1 and 10 micrograms/ml caused dysmorphogenesis but did not inhibit cytodifferentiation which, however, often was poor. Higher concentrations of gentamicin (100 micrograms/ml) had a more generalized toxic effect not only on epithelial but also on mesenchymal tissue.