INTERACTION OF α-MELANOCYTE-STIMULATING HORMONE, MELATONIN, CYCLIC AMP AND CYCLIC GMP IN THE CONTROL OF MELANOGENESIS IN HAIR FOLLICLE MELANOCYTES IN VITRO

In 1981, a study on hair follicle melanocytes in vitro found that α-melanocyte-stimulating hormone (α-MSH) and cyclic AMP increased melanogenesis by enhancing tyrosinase activity. Conversely, cyclic GMP and melatonin inhibited melanin production without reducing tyrosinase activity, suggesting an inhibitory mechanism at a post-tyrosinase step in melanin biosynthesis. Phosphodiesterase inhibitors increased tyrosinase activity while inhibiting melanin production, likely due to the accumulation of cyclic AMP and cyclic GMP. The study proposed that melanogenesis was stimulated by a cyclic AMP-dependent mechanism and inhibited by a cyclic GMP-dependent mechanism, potentially activated by melatonin.