α-Melanocyte Stimulating Hormone in the Modulation of Host Reactions*

Abstract

α-MELANOCYTE-stimulating hormone (αMSH), a basic tridecapeptide, is derived from the precursor molecule POMC(l). The amino acid sequence of αMSH is identical to the 1–13 (N-terminal) amino acid sequence of ACTH although αMSH has little direct influence on glucocorticoid release from the adrenal gland. αMSH is found mainly in the pituitary, but it also occurs in lower concentrations in the central nervous system (CNS), the skin, and other sites (1). This peptide was named for its effect on pigmentation in amphibian skin, although its distribution in tissues of higher organisms suggests that it is important to other functions. Phylogenetically, αMSH is an “ancient” molecule, little changed over the last few hundred million years, and there is remarkable conservation of its amino acid sequence across species. Evidence that this endogenous neuropeptide is important to limitation of fever and inflammation in mammals, including man, suggests that αMSH has retained a role as a modulator of host responses (2–7).