Time-dependent response of vestibular hair cells of guinea pigs following high-dose applications of streptomycin

Apoptosis has been reported to occur in vestibular hair cells following ami noglycoside treatment and is suggested to play a predominant role in deleti on of affected hair cells. However, the type of cell death occurring during an acute phase of vestibular damage following high-dose application of str eptomycin has not yet been determined. Hence, in this study we examined the cell death mode of vestibular hair cells during the acute phase. The numbe rs of hair cell nuclei stained by the terminal deoxynucleotidyl transferase -mediated deoxyuridine triphosphate nick end labelling (TUNEL) method and r esidual hair cells were quantitatively analysed. Hoechst nuclear staining w as used for analysis of the nuclear morphology of affected hair cells. TUNE L staining of hair cell nuclei and lost hair cells began to appear 6 h afte r streptomycin treatment and increased with more exposure time. Apoptotic n uclear features could also be found from 6 h after streptomycin treatment. These findings support the thesis that apoptosis is a predominant cell deat h mode in degeneration of vestibular hair cells due to streptomycin ototoxi city.