Stimulation by melanocyte stimulating hormone and dibutyryl adenosine 3'5'-cyclic monophosphate of DNA synthesis in human melanocytes in vitro.

The proliferation of human melanocytes in vitro was stimulated by MSH. This stimulation was further intensified by the simultaneous addition of theophylline with MSH. Theophylline alone stimulated proliferation moderately. Dibutyryl cyclic AMP strongly stimulated the proliferation, but sodium butyrate, 5'-AMP and cGMP did not. The stimulation by dibutyryl cyclic AMP was continued up to 4 days so far tested. These findings are directly opposed to those on mouse melanoma cells in culture which responded with retarded growth to MSH and cyclic AMP. It is suggested that the difference of proliferation control may explain the different reaction of the melanocyte and the melanoma cells. The epidermal melanocytes seem to belong to the exceptional group of the cells which responded to cyclic AMP with accelerated proliferation.