Effects of dibutyryl adenosine 3',5'-cyclic monophosphate on human melanocytes in vitro

The effects of cyclic AMP and its analogue, dibutyryl cyclic AMP (DBcAMP) on the pigmentary system were studied by using human epidermal melanocytes in culture. The melanocytes responded to 1 mM DBcAMP with an increase in number, length, and complexity of dendritic processes. The effect of DBcAMP on the dendritogenesis was reversible. Melanin synthesis, as indicated by the uptake of tyrosine in the presence of an inhibitor of protein synthesis, was significantly stimulated by DBcAMP. The maximum stimulation was observed at concentrations of 0.5 mM, and 1.0 mM. The melanin synthesis increased after 12-hour treatment with DBcAMP and continued to increase with the prolonged treatment. Cyclic AMP, theophylline, sodium butyrate, or 5'-AMP at a concentration of 1 mM did not have any remarkable effect on the morphology or the melanin synthesis of the melanocyte. The results of this investigation indicate the possible role of the MSH-cyclic AMP system in the melanin pigmentation of human skin and represent a system for further study of the pathobiology of human melanocytes.