title: Glutamate stimulation increases hormone release in rat melanotrophs.
abstract: In melanotrophs, neuroendocrine cells from the intermediate lobe of the rat pituitary gland, glutamate causes a rise in intracellular [Ca2+] suggesting the presence of ionotropic NMDA and non-NMDA AMPA/K receptors. However, the Ca(2+)-dependent release of the major peptide hormone, alpha-melanocyte stimulating hormone (alpha-MSH), in response to glutamate stimulation has not been studied yet in this cell model. Significant spontaneous secretion of the peptide, which results in hormone deposits on the perimeter of the cells, has been confirmed by using confocal microscopy. Co-staining with a membrane area marker FM 1-43, which co-localized with the immunocytochemically marked hormone deposits, showed that fusion-competent sites on the plasma membrane coincided with secretion-competent sites. Stimulation of the cells with glutamate and high K+ saline induced a significant increase in the plasma membrane area covered with alpha-MSH deposits compared to control cells incubated with glutamate and CNQX, a glutamate channel blocker. The optical approach to monitor the secretory activity of a single neuroendocrine cell revealed that glutamate stimulates the release of alpha-MSH at distinct exocytotic membrane domains only.
authors.affiliation: Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Medical Faculty, University of Ljubljana, Zaloska 4, SI-1000 Ljubljana, Slovenia.
authors.forename: Marko
authors.initials: M
authors.lastname: Kreft
authors.forename: Mija
authors.initials: M
authors.lastname: Blaganje
authors.forename: Sonja
authors.initials: S
authors.lastname: Grilc
authors.forename: Marjan
authors.initials: M
authors.lastname: Rupnik
authors.forename: Robert
authors.initials: R
authors.lastname: Zorec
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005089:Exocytosis; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes; D018698:Glutamic Acid / Q000494:pharmacology / Q000502:physiology*; D005998:Glycine / Q000378:metabolism; D018613:Microscopy, Confocal; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D000521:alpha-MSH / Q000378:metabolism*
chemical_list: D018691:Excitatory Amino Acid Antagonists; C073804:FM1 43; D005456:Fluorescent Dyes; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D012965:Sodium Chloride; D000521:alpha-MSH; D011189:Potassium Chloride; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D005998:Glycine