title: Stimulation of catecholamine synthesis by orexin-A in bovine adrenal medullary cells through orexin receptor 1.
abstract: Orexin-A has recently been identified as a new hypothalamic peptide working as a mediator in the regulation of feeding behavior and sleep control. To determine the role of orexin-A in peripheral metabolic processes, we examined direct effects of orexin-A on catecholamine synthesis and secretion in cultured bovine adrenal medullary cells. Incubation of cells with orexin-A (100 pM) for 20 min caused a small but significant increase in 14C-catecholamine synthesis from [14C]tyrosine, but not from L-3,4-dihydroxyphenyl[3-14C]alanine. Orexin-A (100 pM) potentiated the stimulatory effects of acetylcholine (0.3 mM) on 14C-catecholamine synthesis. Orexin-A significantly increased tyrosine hydroxylase activity, which was evident at 1 pM and maximal at 100 pM. 4 beta-Phorbol-12 beta-myristate-13 alpha-acetate, an activator of protein kinase C, did not enhance the stimulatory effects of orexin-A on tyrosine hydroxylase activity, while H-7 and staurosporine, inhibitors of protein kinase C, nullified the effects of orexin-A. Orexin-A had little effect on catecholamine secretion from the cells. Orexin receptor 1 (OX(1)R) but not orexin receptor 2 (OX(2)R) mRNA was detected in bovine adrenal medullary cells by reverse transcriptase-polymerase chain reaction. These findings suggest that orexin-A activates tyrosine hydroxylase and then stimulates catecholamine synthesis, probably via activation of the OX(1)R-protein kinase C pathway in adrenal medullary cells.
authors.affiliation: Department of Pediatrics, University of Occupational and Environmental Health, School of Medicine, 1-1, Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan.
authors.forename: Yasusada
authors.initials: Y
authors.lastname: Kawada
authors.forename: Susumu
authors.initials: S
authors.lastname: Ueno
authors.forename: Kohtaro
authors.initials: K
authors.lastname: Asayama
authors.forename: Masato
authors.initials: M
authors.lastname: Tsutsui
authors.forename: Kensuke
authors.initials: K
authors.lastname: Utsunomiya
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Toyohira
authors.forename: Naoya
authors.initials: N
authors.lastname: Morisada
authors.forename: Kazumi
authors.initials: K
authors.lastname: Tanaka
authors.forename: Akira
authors.initials: A
authors.lastname: Shirahata
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yanagihara
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000313:Adrenal Medulla / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D000818:Animals; D002250:Carbon Radioisotopes; D002352:Carrier Proteins / Q000494:pharmacology*; D002395:Catecholamines / Q000096:biosynthesis*; D002417:Cattle; D002478:Cells, Cultured; D004295:Dihydroxyphenylalanine / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides / Q000494:pharmacology*; D064446:Orexin Receptors; D000068797:Orexins; D011493:Protein Kinase C / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide / Q000378:metabolism*; D013997:Time Factors; D014443:Tyrosine / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D002352:Carrier Proteins; D002395:Catecholamines; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D014443:Tyrosine; D004295:Dihydroxyphenylalanine; D014446:Tyrosine 3-Monooxygenase; D011493:Protein Kinase C; D000109:Acetylcholine