Fig. 2.

Cochlear hair cell loss occurred after 48 h exposure to low, but not high concentrations of cisplatin. (A) Representative confocal photomicrographs showing inner (IHC) and outer hair cells (OHC) in the middle turn of the cochlear basilar membrane of control and cisplatin-treated (10, 50, 100, 400 or 1000 μM) cultures. Note the severe hair cell loss following 48 h exposure to 50 μM cisplatin (Cis50), whereas most hair cells were intact following high concentrations of cisplatin (Cis400 and Cis1000). Scale bar shown in upper left panel represents 10 μm. (B) Mean cochleograms for each treatment condition (control, 10, 50, 100, 400 or 1000 μM cisplatin) show the degree of hair cell loss as a function of the percent distance from the apex of the cochlea. Hair cell loss was fairly uniform throughout the length of the cochlea following exposure to 10, 50 and 100 μM cisplatin. The minor hair cell loss observed at each end of the basilar membrane in the control, 400 and 1000 μM cisplatin-treated cultures was an artifact associated with the surface preparation. (C) Comparison of the mean number of surviving hair cells (measured between 20% and 80% of the distance from the apex) for each treatment condition revealed unexpectedly that low concentrations of cisplatin (10, 50 and 100 μM) were more ototoxic than high concentrations (400 and 1000 μM).