title: Melatonin receptors in the chicken kidney are up-regulated by pinealectomy and linked to adenylate cyclase.
abstract: The effect of pinealectomy on the characteristics of melatonin receptors in the chicken kidney was studied. One-day-old chicks were operated and kept under a 12 h/12 h light/dark photoperiod. Six weeks after operation, the animals were sacrificed at mid-light and mid-dark. Serum melatonin was determined by radioimmunoassay and kidney melatonin receptors were studied by radioreceptor assay using the melatonin agonist 2-[125I]iodomelatonin as the radioligand. Pinealectomy significantly reduced the mid-dark serum melatonin level and abolished the diurnal rhythm of 2-[125I]-iodomelatonin binding in the kidney. The density of 2-[125I]-Iodomelatonin binding sites in the kidney at mid-dark was increased significantly to a value comparable to the mid-light density after pineal ablation. Our results suggest that melatonin receptors in the chicken kidney are directly regulated by melatonin in the circulation. The coupling of kidney melatonin receptors to adenylate cyclase was investigated. The basal and forskolin-stimulated cAMP production in chicken kidney explants was studied following melatonin or melatonin plus pertussis toxin treatment. Levels of cAMP in chicken kidney explants were extracted and determined by radioimmunoassay. Melatonin had no effect on basal cAMP levels. However, melatonin significantly inhibited the forskolin-stimulated cAMP accumulation at a concentration of 10 pmol/l. Inhibitory effects of melatonin on the forskolin-stimulated cAMP increase in the chicken kidney were totally blocked by preincubating the kidney tissue with 1.0 micrograms/ml pertussis toxin. Our results suggest that kidney melatonin receptors may modulate the adenylate cyclase leading to biological responses in the renal system.
authors.affiliation: Clarke Institute of Psychiatry, Toronto, Ontario, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Song
authors.forename: C S
authors.initials: CS
authors.lastname: Pang
authors.forename: E A
authors.initials: EA
authors.lastname: Ayre
authors.forename: G M
authors.initials: GM
authors.lastname: Brown
authors.forename: S F
authors.initials: SF
authors.lastname: Pang
mesh_terms: D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002645:Chickens / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D008550:Melatonin / Q000031:analogs & derivatives / Q000378:metabolism; D037342:Pertussis Toxin; D010870:Pineal Gland / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D044094:Receptors, Melatonin; D015854:Up-Regulation; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D037361:Adenylate Cyclase Toxin; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin; D010566:Virulence Factors, Bordetella; C044556:2-iodomelatonin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D000262:Adenylyl Cyclases; D008550:Melatonin