CHARACTERIZATION OF MELANOGENESIS AND MORPHOGENESIS OF MELANOSOMES BY PHYSICOCHEMICAL PROPERTIES OF MELANIN AND MELANOSOMES IN MALIGNANT-MELANOMA

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  • 1 January 1984
    • journal article
    • research article
    • Vol. 44  (3) , 1128-1134
Abstract
This study elucidates the nature of melanogenesis in B16 and Harding-Passey (HP) mouse melanomas producing melanin and melanosomes of different color and fine structure, i.e., brown-black eumelanosome-like B16 granules and reddish brown pheomelanosome-like HP granules, and compares them with typical 3,4-dihydroxyphenylalanine (DOPA) and sepia eumelanins and sepia eumelanosomes. The melanin content of B16 melanosomes was more than 3 times higher than that of HP melanosomes. The content of free and protein-bound DOPA and 5-S-cysteinyldopa varied greatly in B16, HP and sepia melanosomes and was unrelated to melanin content. Chemical analysis of the eumelanin:phenomelanin ratio in melanosomes and elemental analysis of isolated melanin showed that B16 and HP melanins are primarily eumelanic, with a higher ratio of pheomelanic component in HP melanin. The spectra of ESR and IR and X-ray small-angle scattering of B16 and HP melanins were basically similar to those of sepia and DOPA melanins. B16, HP and DOPA melanins were dissolved in aqueous NH3, while sepia melanin was dissolved to a far lesser extent. B16 and HP melanomas are primarily involved in eumelanogenesis, although the fine structure of their melanosomes is entirely different. The marked color difference in the 2 melanosomes is related to a difference in the absolute content of eumelanin, the presence of a small amount of pheomelanin, and the mode of chemical bindings of melanin to structural proteins. In contrast to normal skin and hair, melanosome morphogenesis may not directly correspond to melanogenesis type in malignant melanoma.