title: Analysis of autofeedback mechanisms in the secretion of pro-opiomelanocortin-derived peptides by melanotrope cells of Xenopus laevis.
abstract: The secretion of most pituitary hormones is under the control of feedback mechanisms. The feedback control of alpha-melanophore-stimulating hormone (alpha-MSH) from melanotrope cells is controversial. The possible existence of an autofeedback exerted by alpha-MSH or other POMC-derived peptides on melanotrope cells of the amphibian Xenopus laevis has been investigated. alpha-MSH or its potent agonist 4-norleucine,7-D-phenylalanine-alpha-MSH has no effect on the release of radiolabeled POMC-derived peptides or immunoreactive beta-endorphin from superfused neurointermediate pituitary lobes. Melanin concentrating hormone, previously reported to have an alpha-MSH-like effect on melanophores, did not affect alpha-MSH secretion. Neurointermediate lobe superfusate, which contains a mixture of POMC-derived peptides, failed to affect the secretory activity of melanotropes. It is concluded that in X. laevis the secretory activity of melanotropes is not under the control of short-term autofeedback mechanisms involving alpha-MSH or other POMC-derived peptides.
authors.affiliation: Department of Animal Physiology, Faculty of Science, University of Nijmegen, The Netherlands.
authors.forename: H P
authors.initials: HP
authors.lastname: de Koning
authors.forename: B G
authors.initials: BG
authors.lastname: Jenks
authors.forename: W J
authors.initials: WJ
authors.lastname: Scheenen
authors.forename: P H
authors.initials: PH
authors.lastname: Balm
authors.forename: E W
authors.initials: EW
authors.lastname: Roubos
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D005246:Feedback; D007457:Iodine Radioisotopes; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism*; D000521:alpha-MSH / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D001615:beta-Endorphin / Q000378:metabolism
chemical_list: D007457:Iodine Radioisotopes; D000521:alpha-MSH; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin; C027756:MSH, 4-Nle-7-Phe-alpha-