Figure 1. Dose-dependent effects of -MSH, 1, 2, and 3 on tyrosinase activity of cultured human melanocytes. Melanocytes were plated into 60 mm culture dishes and treated for a total of 6 d with increasing doses of melanocortin peptides (0 [control]-100 nM). Tyrosinase activity was determined in triplicate dishes/group. SE for each data point was less than 10%. Each peptide was tested at least twice on different melanocyte cultures, with similar results.