Abstract
According to a recent hypothesis the melanin granules in the retinal pigment epithelium of mammals originate from photosensory membrane degradation. To test this hypothesis the retinal pigment epithelium of cattle was kept in tissue culture and exposed to gold-labelled rod outer segments. Gold granules were later detected inside phagosomes, melanosomes and mature melanin granules. Tyrosinase, the key enzyme in melanogenesis, was additionally localized inside phagosomes. These results indicate that in cultured retinal pigment epithelium the matrix of the melanosome can originate from phagosomes. Therefore, the melanosome is a specialized lysosome.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Biomarkers
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Cattle
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Cell Communication
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Cells, Cultured
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Cytoplasmic Granules / enzymology
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Cytoplasmic Granules / ultrastructure
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Eye Proteins / analysis
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Gold
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Intracellular Membranes / metabolism
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Intracellular Membranes / ultrastructure
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Lysosomes / physiology*
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Melanins / biosynthesis*
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Melanocytes / chemistry
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Melanocytes / physiology*
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Microscopy, Electron
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Models, Biological
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Monophenol Monooxygenase / analysis
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Peroxidase / analysis
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Phagocytosis*
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Photoreceptor Cells / metabolism
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Pigment Epithelium of Eye / metabolism*
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Pigment Epithelium of Eye / ultrastructure
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Rod Cell Outer Segment / metabolism
Substances
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Biomarkers
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Eye Proteins
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Melanins
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Gold
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Peroxidase
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Monophenol Monooxygenase