Electron Microscopic and Cytochemical Observations of Theophylline and Melanocyte-stimulating Hormone Effects on Melanoma Cells in Culture¹

The effects of theophylline and melanocyte-stimulating hormone on B16 melanoma cells in culture were studied by electron microscopy and dopa cytochemistry. The data show that theophylline and melanocyte-stimulating hormone enhance melanogenesis by activating tyrosinase synthesis and its transfer but that neither affects the synthesis of the well-organized eumelanosome matrix. Their pigmenting effects appear to be limited to the melanogenic cells and result from a marked increase, particularly in theophylline-treated cells, in pheomelanosome formation.