Early Ultrastructural Effects of Gentamicin Cochleotoxicity

Abstract

Ultrastructural changes in the cochlear hair cells during the early stages of gentamicin intoxication were investigated after trialdehyde primary fixation and OsO₄/K₄Ru(CN)₆ post-fixation. In cochleas treated for 5,10 and 15 days with gentamicin the individual outer hair cells (OHC₁, OHC₂ and OHC₃) were randomly affected. Degeneration of the inner hair cells was not observed at this stage. Ultrastructurally, the earliest identifiable changes were an increase in lysosomes, proliferation of the endoplasmic reticulum, and formation of Hensen's bodies. This was followed by dilatation of the endoplasmic reticulum and the nuclear envelope, giving rise to extensive cytoplasmic vacuolation. These results demonstrate that gentamicin-induced changes primarily involve the cell's synthetic apparatus. AH further intracellular changes occur at a much later stage and are therefore to be considered secondary events.

Key Words:

• cochlea
• hair cell pathology
• aminoglycoside cochleotoxicity
• gentamicin