Effects of Alpha-Melanocyte-Stimulating Hormone and [8-Arginine]-Vasotocin on Melanogenesis in Hair Follicle Melanocytes In Vitro

The study demonstrated that α-melanocyte-stimulating hormone (α-MSH) directly stimulated melanogenesis in hair follicle melanocytes from Siberian hamsters by increasing tyrosinase activity, but only in follicles from moulting animals, indicating a cycle-dependent expression of MSH receptors. Synthetic 1–24 ACTH did not affect melanogenesis. The pineal peptide [8-arginine]-vasotocin (AVT) inhibited melanin production without reducing tyrosinase activity, suggesting its action occurs post-tyrosinase in melanin biosynthesis. AVT's effects were specific, as similar peptides like oxytocin and [8-arginine]-vasopressin showed no activity, indicating AVT binds to specific receptors in these melanocytes.