Frog glomerular vasotocin receptors resemble mammalian V1b receptors

• Published in: The American journal of physiology Vol. 267; no. 5 Pt 2; p. R1198
• Main Authors: Ammar, A, Rajerison, R M, Roseau, S, Bloch-Faure, M, Butlen, D
• Format: Journal Article
• Language: English
• Published: United States 01.11.1994
• Subjects: Animals; Binding, Competitive; Female; Inositol - metabolism; Iodine Radioisotopes; Kidney Glomerulus - metabolism; Kinetics; Male; Mammals; Nephrons - metabolism; Phosphoric Diester Hydrolases - metabolism; Radioligand Assay; Rana ridibunda; Receptors, Vasopressin - metabolism; Sex Characteristics; Sex Factors; Structure-Activity Relationship; Vasotocin - analogs & derivatives; Vasotocin - metabolism; Vasotocin - pharmacology
• ISSN: 0002-9513
• DOI: 10.1152/ajpregu.1994.267.5.R1198

Vasotocin receptors were investigated in glomeruli and nephron segments microdissected from collagenase-treated kidneys of Rana ridibunda, using [d(CH2)5Tyr(Me)2,Thr4,Orn8,125I-Tyr-NH2(9)]vasotocin (125I-OVTA) as a radioligand. Specific 125I-OVTA binding sites were found only in glomeruli and not in all tubule segments tested. Glomerular receptors exhibited the following stereospecificity for recognition of vasotocin analogues: Tyr-NH2(9)-LA-V1a > 125I-OVTA > arginine vasotocin (AVT) > or = [d(CH2)5Tyr-(Me)2]AVP > OVTA > or = [Phe2,Orn8]VT > oxytocin (OT) > or = [d(CH2)5-Sar7]AVP > desGly9[d(CH2)5Tyr(Et)2]VAVP > or = [d(CH2)5Tyr(Et)2]VAVP > AVP > [1-desamino-8-D-arginine]vasopressin (DDAVP) > [Thr4,Gly7]OT. In addition, vasotocin enhanced [3H]inositol phosphate production in sieved glomeruli labeled with myo-[3H]inositol; the rank order of structural vasotocin analogues for stimulation of phosphoinositidase C was [Phe2,Orn8]VT > AVT > OT > AVP > DDAVP, whereas [Thr4,Gly7]OT was almost inactive, and the rank order of antagonists for inhibition of hormone-induced enzyme activation was Tyr-NH2(9)-LA-V1a > [d(CH2)5Tyr(Me)2]AVP = OVTA > [d(CH2)5Sar7]AVP > [d(CH2)5Tyr(Et)2]VAVP > or = desGly9[d(CH2)5Tyr(Et)2]VAVP. Results indicate that the 125I-OVTA-labeled binding sites detected in frog glomeruli reveal the pharmacological properties of mammalian V1b-pituitary vasopressin receptors and might be physiological vasotocin receptors involved in phosphoinositidase C stimulation.