Influence of gamma irradiation on developing otoconia.

Thirty-two CBA/CBA mice were irradiated in utero on the 12th, 13th, or 16th gestational day with doses of 0.5, 1, and 2 Gy, respectively (1 Gy = 100 rads). One month after birth, the inner ears were examined by light microscopy and transmission and scanning electron microscopy. Otoconia with defective shapes was identified frequently. The strict hexagonal shape of normal otoconia seldom developed and, in exposed animals, had often been replaced with rounded, oval, or elongated shapes. The otoconial substructure was disarrayed, and fusion of two or three otoconia occurred. Degenerating otoconia appeared in the intercellular space of the dark-cell epithelium. Fetal gross structures of otoconia persisted into maturity.