The present studies were performed to evaluate the transplacental ototoxic effect of 3', 4-dideoxykanamycin B (DKB), kanamycin (KM) and gentamicin (GM) on the inner ears in the intrauterine guinea pig embryos.
Intramuscular administration of the individual antibiotics to the pregnant guinea pigs of the Hartley strain started on the first day of the pregnancy. DKB was given at the doses of 100 mg/kg for 58-60 days or 75 mg/kg for 58-59 days, KM at the doses of 300 mg/kg for 58-60 days or 200 mg/kg for 53-61 days and GM at the doses of 100 mg/kg for 28 days or 40 mg/kg for 57-59 days, respectively.
The concentration of DKB and KM in the placenta, amniotic fluid and the liver and kidney of the intrauterine guinea pig embryos was measured by bioassay and it was revealed that these antibiotics can pass from the maternal guinea pigs to the intrauterine embryos.
Histopathologic examination of the new-born guinea pigs at the one month after birth disclosed that the most frequent damage of the inner ear in the new born guinea pigs was the loss of the outer hair cells confined to the organ of CORTI at the basal end of the first turn of the cochlea (40%). Relatively localized hypoplasia of the spiral ganglion in the upper part of the 4. turn associated with the mild displasia of the regional organ of CORTI occurred in 11% in the new born guinea pigs delivered from the maternal ones received DKB 75 mg/kg. The disappearance of the organ of CORTI relatively localized at the 3. turn of the cochlea was found in one guinea pig delivered from the maternal one received DKB 100 mg/kg. There was no remarkable pathologic change in the vestibular organs in the new-born guinea pigs.
