In vivo biosynthesis of melanotropins and related peptides in the pars intermedia of Xenopus laevis.
To study in vivo biosynthesis of pars intermedia peptides in Xenopus laevis, [3H]lysine was administered by an osmotic minipump via a cannula inserted near the pituitary gland. Following extraction of the neurointermediate lobe, high-performance liquid chromatography was used to separate the newly synthesized peptides. In black-background adapted animals, [3H]lysine was incorporated into a number of peptides. The elution characteristics of these peptides corresponded exactly with those of peptides synthesized during in vitro incubation of neurointermediate lobes, and which were identified as des-N alpha-acetyl-alpha-MSH, a gamma-MSH-like peptide, two corticotropin-like intermediate lobe peptides, and two forms of endorphin. In white-background adapted Xenopus, practically no synthesis of pars intermedia peptides occurred. Transfer of black-adapted toads to a white background at the beginning of infusion led to storage of newly synthesized peptides. When such animals were maintained on a white background for 10 days, des-N alpha-acetyl-alpha-MSH, but not alpha-MSH, was present in the pars intermedia; this supports the notion that des-N alpha-acetyl-alpha-MSH constitutes the "storage form" of alpha-MSH.
D000222:Adaptation, Physiological; D000324:Adrenocorticotropic Hormone / Q000096:biosynthesis; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D053497:Corticotropin-Like Intermediate Lobe Peptide; D004723:Endorphins / Q000096:biosynthesis; D004777:Environment; D008239:Lysine / Q000378:metabolism; D009074:Melanocyte-Stimulating Hormones / Q000096:biosynthesis*; D010446:Peptide Fragments / Q000096:biosynthesis; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism*
D004723:Endorphins; D010446:Peptide Fragments; D053497:Corticotropin-Like Intermediate Lobe Peptide; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones; D008239:Lysine