Interaction of Alpha-Melanocyte-Stimulating Hormone, Melatonin, Cyclic AMP and Cyclic GMP in the Control of Melanogenesis in Hair Follicle Melanocytes In Vitro

In this study, short-term cultures of hair follicles demonstrated 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, and they counteracted the effects of cyclic AMP and α-MSH on melanin production. Phosphodiesterase inhibitors stimulated tyrosinase activity while inhibiting melanin production, likely due to the accumulation of cyclic AMP and cyclic GMP. The findings suggested that melanogenesis was stimulated by a cyclic AMP-dependent mechanism, while an inhibitory cyclic GMP-dependent mechanism, potentially activated by melatonin, operated at a post-tyrosinase step in the melanin biosynthetic pathway.