EFFECT OF α-MSH ON THE TYROSINASE ACTIVITY AND THE RATE OF MELANIN ACCUMULATION OF MELANOMA CELLS IN VITRO

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Abstract
A stimulation of the tyrosinase activity was observed when melanoma cells isolated from transplantable mouse melanomas were incubated at 37°C for 6 h in the presence of 1–10 × 10−6 m α-MSH. All strains of mouse melanomas studied (B-16, Cloudman S-91 and Harding-Passey), exhibited similar responses. It was also observed that the intact cellular structure of melanoma cells was not required for the ability to respond to α-MSH. The stimulation of the enzymic activity was accompanied by an increase of the rate of incorporation of radioactivity into melanin from L-[U-14C]tyrosine, indicating an enhanced melanogenesis of tumour cells under in vitro conditions.