Frog glomerular vasotocin receptors resemble mammalian V1b receptors.
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.
Ammar
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Laboratoire de Physiologie Cellulaire, Unité de Recherche Associée 219, Centre National de la Recherche Scientifique, Collège de France, Paris.
Rajerison
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RM
Roseau
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Bloch-Faure
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Butlen
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D000818:Animals; D001667:Binding, Competitive; D005260:Female; D007294:Inositol / Q000378:metabolism; D007457:Iodine Radioisotopes; D007678:Kidney Glomerulus / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008322:Mammals; D009399:Nephrons / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011869:Radioligand Assay; D011895:Rana ridibunda; D017483:Receptors, Vasopressin / Q000378:metabolism*; D012727:Sex Characteristics; D012737:Sex Factors; D013329:Structure-Activity Relationship; D014668:Vasotocin / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology
D007457:Iodine Radioisotopes; D017483:Receptors, Vasopressin; C034862:vasotocin receptor; C076093:vasotocin, (beta-mercapto-beta,beta-cyclopentamethylenepropionic acid)-O-methyl-Tyr(2)-Thr(4)-Orn(8)-Tyr(9)-NH2; D007294:Inositol; D010727:Phosphoric Diester Hydrolases; C021491:glycerophosphoinositol glycerophosphodiesterase; D014668:Vasotocin