title: Oxytocin receptors from LLC-PK1 cells: expression in Xenopus oocytes.
abstract: Two selective radioligands for oxytocin receptors, [3H]-[4-threonine,7-glycine]oxytocin [( 3H]-[Thr4,Gly7]OT) and 125I-[1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine, 4-threonine, 8-ornithine, 9-tyrosine amide]-oxytocin (125I-OTA), were used to characterize oxytocin receptors from two pig kidney-derived cell lines, LLC-PK1 and LLC-PK1L. [3H]-[Thr4,Gly7]OT and 125I-OTA bind with high affinity (mean Kd values of 14 and 0.06 nM, respectively) to the same population of sites on LLC-PK1 cell membranes [maximum binding (Bmax) of 100 fmol/mg membrane protein]. These sites had the expected ligand selectivity of oxytocin receptors. [3H]-[Thr4,Gly7]OT and 125I-OTA binding sites could be distinguished from V2 vasopressin receptors present on LLC-PK1 and LLC-PK1L cells on the basis of clearly different maximal capacities and ligand selectivities, different sensitivities to insulin and serum, and absence of heterologous downregulation. Oxytocin receptors from LLC-PK1 cells have no functional relationship with adenylate cyclase. [Thr4,Gly7]OT affected neither the basal adenosine 3',5'-cyclic monophosphate (cAMP) content nor the vasopressin-induced cAMP accumulation by LLC-PK1 cells. Xenopus laevis oocytes injected with LLC-PK1 cell mRNA responded to [Thr4,Gly7]OT by an increase in 45Ca2+ outflux; this effect is antagonized by a highly selective oxytocin antagonist.
authors.affiliation: Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Medicale de Pharmacologie-Endocrinologie, Montpellier, France.
authors.forename: B
authors.initials: B
authors.lastname: Cantau
authors.forename: J N
authors.initials: JN
authors.lastname: Barjon
authors.forename: D
authors.initials: D
authors.lastname: Chicot
authors.forename: P P
authors.initials: PP
authors.lastname: Baskevitch
authors.forename: S
authors.initials: S
authors.lastname: Jard
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D005260:Female; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D008024:Ligands; D008236:Lypressin / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism*; D010121:Oxytocin / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011945:Receptors, Angiotensin / Q000378:metabolism*; D018045:Receptors, Oxytocin; D013552:Swine; D014667:Vasopressins / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: C055830:KB 5-21; D008024:Ligands; D012333:RNA, Messenger; D011945:Receptors, Angiotensin; D018045:Receptors, Oxytocin; D014667:Vasopressins; D010121:Oxytocin; D008236:Lypressin; D000242:Cyclic AMP; D003894:Deamino Arginine Vasopressin; D002118:Calcium