Characterization of melanosomes and melanogenesis in cells cultured from Ota's nevus.

Cells from dermis and epidermis of Ota's nevus lesions were cultured to obtain the pigment producing cells that are specific epidermal and dermal melanocytes of nevus Ota. The following media were used: Eagle's minimum essential medium, fortified or not fortified with cholera toxin and phorbol ester. Both epidermal melanocytes and dermal melanocytes grew in the Eagle's minimum essential medium fortified with cholera toxin and phorbol ester. The melanocytes were characterized by 14C-tyrosine uptake and by identification of melanosomes and status of melanogenesis in comparison with those reported in dysplastic nevi and melanomas, as well as those found in Ota's nevus tissue in situ. Eumelanosomes, pheomelanosomes and secondary lysosomal melanosomes appeared in epidermal melanocytes. Pheomelanosomes and melanolysosomes, or myelinosiderosomes appeared predominantly in the dermal melanocytes. These melanosomes seemed to be related to the peculiar skin color of nevus Ota. Some of the abnormal types of melanosomes were very similar to those found in dysplastic nevi and melanomas.