ABSTRACT
A major secretory product of the pars intermedia of the pituitary gland is the melanotropic peptide alpha-melanophore-stimulating hormone. Most amphibians possess the remarkable ability to alter the color of their skin by altering the distribution of pigment in pigment-containing cells (chromatophores) of their integument. Pro-opiomelanocortin (POMC) was first characterized in a mouse pituitary tumor-cell line, but it was soon shown to be produced by a number of different tissues including endocrine cells of the pituitary gland and within neuronal networks of the central nervous system (CNS). The physiological significance of a POMC cell will be determined largely by the nature of its secretory signal, considered both qualitatively and quantitatively. Knowledge of the regulatory mechanisms involved in the generation and release of these diverse biological signals will contribute to an understanding of neuronal and neuroendocrine communication. The presence of a precursor to α-MSH in amphibians was first demonstrated in the species Xenopus laevis..
