MELANOGENESIS IN CULTURED MELANOCYTES CAN BE SUBSTANTIALLY INFLUENCEDBY L-TYROSINE AND L-CYSTEINE

We investigated the effect of varying concentration of 1-tyrosine and 1-cysteine in culture medium on melanin production by human skin melan ocytes (skin phototype II/III), In addition to the analyses of dopa ox idase activity and total melanin, pheomelanin production in the cells was assessed by high-performance liquid chromatography determinations of pheomelanin degradation products, 3-aminotyrosine and 4-amino-3-hyd roxyphenylalanine. As another marker for pheomelanin, melanosomal sulf ur was determined by the use of X-ray microanalysis, With varying conc entration of both amino acids, profound changes in the pigmentation pa tterns of the melanocytes were observed. A high concentration of 1-tyr osine (0.2 mM) was always connected with increased pigmentation. In co mbination with a low 1-cysteine content: we saw an increase in tyrosin ase activity and the highest melanin content, At: high concentrations of both I-tyrosine and I-cysteine, the melanocytes showed reduced tyro sinase activity and they produced notably more pheomelanin. In case of the pheomelanin measurements by high-performance liquid chromatograph y and the sulfur detection with X-ray microanalysis, strongly increase d concentrations were found when cells were maintained in high 1-tyros ine medium as compared with those grown with low 1-tyrosine, This was especially true for the combination with low 1-cysteine showing that t he l-tyrosine content of the medium strongly influences not only the e umelanin bur also the pheomelanin production in the cultured melanocyt e. It can be concluded that variations in;he concentrations of 1-tyros ine and I-cysteine in culture medium can be used to regulate the melan ogenetic phenotype under in vitro conditions.