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Effect of gentamycin on vestibular dark cells and melanocytes: an ultrastructural and cytochemical study
T Yoshihara1, H Kaname, T Ishii
1Department of Otolaryngology, Tokyo Women's Medical College, Japan.
Abstract:
Vestibular dark cells areas in gentamycin (GM)-intoxicated guinea pigs were examined ultrastructurally and cytochemically. After GM treatment the dark cells represented cytoplasmic vacuoles, wide intercellular space, less osmiophilic cytoplasm and irregularly shaped basal portions. Cytochemically, Na+,K(+)-ATPase activity was demonstrated on the basolateral folded plasma membranes of the dark cells similarly in both GM-intoxicated and control guinea pigs. These findings revealed that the dark cells still possessed a function of regulating the ionic composition of the endolymph, although they showed various structural changes. On the other hand, the melanocytes extended their cytoplasmic processes into the basement membrane and the intercellular space of the dark cells. Melanosomes markedly increased in number dose-dependently by GM treatment. The significance and the function of the melanocytes in the dark-cell areas are discussed.
Insights
Gentamicin (GM) causes structural changes in vestibular dark cells, but they retain their ion-regulating function. Melanocytes in these areas increase in number and extend processes after GM exposure.
Area of Science:
- Ototoxicology
- Cell Biology
- Neuroscience
Background:
- Vestibular dark cells are crucial for endolymph homeostasis.
- Gentamicin (GM) is a known ototoxic agent affecting inner ear structures.
- The role of melanocytes in vestibular dark cell areas is not fully understood.
Purpose of the Study:
- To investigate the ultrastructural and cytochemical effects of gentamicin on vestibular dark cells and melanocytes in guinea pigs.
- To assess the functional integrity of vestibular dark cells after GM intoxication.
- To explore the changes in melanocytes within the vestibular dark cell areas following GM exposure.
Main Methods:
- Ultrastructural examination of vestibular dark cells and melanocytes.
- Cytochemical demonstration of Na+,K(+)-ATPase activity.
- Dose-dependent analysis of melanosome changes.
Main Results:
- Gentamicin induced cytoplasmic vacuoles, wider intercellular spaces, and altered basal portions in dark cells.
- Na+,K(+)-ATPase activity persisted on the basolateral membranes of dark cells, indicating retained function.
- Melanocytes extended cytoplasmic processes into the basement membrane and intercellular spaces.
- Melanosome numbers increased dose-dependently with GM treatment.
Conclusions:
- Vestibular dark cells maintain their ion-regulatory function despite structural damage from gentamicin.
- Melanocytes exhibit altered morphology and increased melanosome content in response to gentamicin.
- Further research is needed to elucidate the specific role of melanocytes in gentamicin-induced vestibular changes.