Synthesis of a cyclic melanotropic peptide exhibiting both melanin-concentrating and -dispersing activities.

A putative melanin-concentrating hormone was synthesized. This peptide, H-Asp-Thr-Met-Arg-Cys-Met-Val-Gly-Arg-Val-Tyr-Arg-Pro-Cys-Trp-Glu-Val-OH , stimulates melanin granule aggregation within teleost melanocytes at nanomolar concentrations as does the natural purified teleost pituitary preparation. In addition, this peptide stimulates melanin granule dispersion within melanocytes of frogs and lizards. The peptide has about one six-hundredth of the activity of alpha-melanocyte-stimulating hormone on frog and lizard melanocytes and is a full agonist.