125I-labelled d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT: a selective oxytocin receptor ligand.
An oxytocic antagonist, [1-(beta-mercapto-beta, beta-cyclopentamethylenepropionic acid,2-O-methyltyrosine,4-threonine, 8-ornithine,9-tyrosylamide]vasotocin (d(CH2)5[Tyr(Me)2, Thr4,Tyr-NH2(9)]OVT [corrected], was monoiodinated at the phenyl moiety of the tyrosylamide residue at position 9. 125I-labelling was performed with 1,3,4,6-tetrachloro-3 alpha,6 alpha-diphenyl-glycoluril. Iodination resulted in an increased affinity for rat uterine oxytocin receptors. A considerably lower affinity for rat vascular V1- and renal V2-receptors was found, resulting in a highly specific oxytocin receptor ligand. 125I-labelled d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT [corrected] was demonstrated to bind selectively to one population of binding sites in rat uterus and ventral hippocampal membrane preparations. Dissociation constants ranged between 0.03 and 0.06 nM. After 3 days of exposure autoradiography revealed binding in regions known to contain oxytocin receptors as well as labelling in some new regions, while no binding was found in the lateral septum, a structure containing mainly [8-arginine]vasopressin receptors. The high specific radioactivity of 125I-labelling allowed important reductions in membrane protein amount, gain in precision of binding analysis as well as considerably lower exposure times for autoradiography.
Elands
J
J
Centre CNRS-INSERM de Pharmacologie-Endocrinologie, Montpellier, France.
Barberis
C
C
Jard
S
S
Tribollet
E
E
Dreifuss
J J
JJ
Bankowski
K
K
Manning
M
M
Sawyer
W H
WH
D000818:Animals; D001345:Autoradiography; D001923:Brain Chemistry; D002851:Chromatography, High Pressure Liquid; D005260:Female; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D007668:Kidney / Q000378:metabolism; D008024:Ligands; D008099:Liver / Q000378:metabolism; D010121:Oxytocin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011945:Receptors, Angiotensin / Q000378:metabolism*; D018045:Receptors, Oxytocin; D014599:Uterus / Q000378:metabolism
D007457:Iodine Radioisotopes; C055830:KB 5-21; D008024:Ligands; D011945:Receptors, Angiotensin; D018045:Receptors, Oxytocin; D010121:Oxytocin