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Electron microscopical observations of melanin in the endolymphatic sac
K Fukazawa1, M Sakagami, M Umemoto
1Department of Otolaryngology, Kinki Central Hospital, Hyogo, Japan.
Abstract:
Endolymphatic sacs of pigmented guinea pigs were examined by light and electron microscopy. Melanocytes were located not only in the subepithelial connective tissue but also in the intercellular spaces between the epithelial cells. They projected their dendrites into the epithelium extensively. Melanosomes in several stages of maturation and well-developed Golgi apparatus were seen in the cytoplasm of the melanocytes. Melanosomes were also observed in the membrane-bound vacuoles of the epithelial cells. These findings suggest that melanocytes in the endolymphatic sac are highly capable of producing tyrosinase, synthesizing melanin and transferring melanosomes to the epithelial cells, while melanocytes in the other parts of the inner ear do not show signs of melanogenesis under normal conditions.
Insights
Melanocytes in the endolymphatic sac actively produce melanin and transfer it to epithelial cells. This contrasts with other inner ear regions where melanogenesis is not observed under normal conditions.
Area of Science:
- Oto-science
- Cell Biology
Background:
- The endolymphatic sac is a crucial component of the inner ear.
- Melanocytes are pigment-producing cells found in various tissues.
Purpose of the Study:
- To investigate the presence and activity of melanocytes within the endolymphatic sac of pigmented guinea pigs.
- To determine the capacity of these melanocytes for melanin synthesis and melanosome transfer.
Main Methods:
- Light and electron microscopy were utilized to examine endolymphatic sac tissues.
- Cellular structures and melanosome presence were analyzed at a ultrastructural level.
Main Results:
- Melanocytes were identified in both subepithelial connective tissue and intercellular spaces of the endolymphatic sac epithelium.
- These melanocytes exhibited extensive dendritic projections into the epithelium.
- Melanosomes at various maturation stages and active Golgi apparatus were observed in melanocytes, indicating active melanogenesis.
- Melanosomes were also found within membrane-bound vacuoles of epithelial cells, suggesting transfer.
Conclusions:
- Melanocytes in the endolymphatic sac are highly active in tyrosinase production, melanin synthesis, and melanosome transfer to epithelial cells.
- This activity differs from melanocytes in other inner ear regions, which do not show melanogenesis under normal conditions.