[Carboplatin-induced injury patterns of inner hair cells missing in chinchilla cochlea]

To explore carboplatin-induced injury patterns of inner hair cells (IHCs) in cochlea of chinchilla, namely, when injury of IHCs occurs, what extension injury of IHCs exists at different time after drug administration, where maximal injury of IHCs locates on basal membrane and how long most IHCs lose after drug administration.

Carboplatin of moderate concentration (100 mg/kg) was used to inject peritoneally one time and animals were decapitated on schedule, surface preparations were made and cochleograms were obtained to observe injury of IHCs in the cochleae of chinchillas.

Loss of outer hair cells was not observed on basal membrane from 24 hours to 3 months after drug administration except one ear. The characteristic of IHCs injury patterns was found to be: (1) IHCs were intact at 24 hours after drug administration. IHCs injury was firstly observed within 3 days. (2) The maximal rate of IHCs injury located around boundary of turn one and turn two on basal membrane from 24 hours to 3 months. (3) IHCs injury began from boundary of turn one and turn two and extended to basal turn and apical turn gradually. Compared to apical turn, IHCs injury on basal turn occurred earlier and more severely. (4) Most IHCs lost in 3 months.

Carboplatin of 100 mg/kg unequally destroyed IHCs from different turns. Temporal variance of injury of IHCs from given turn is most likely due to their discrepant sensitivity to carboplatin.