title: Linear V1-vascular vasopressin antagonists suitable for radioiodination, biotinylation, and fluorescent labeling.
abstract: We modified several linear V1-vascular arginine vasopressin (AVP) antagonists to obtain compounds suitable for radioiodination, biotinylation, and fluorescent labeling. In binding competition experiments with human platelet V1-vascular AVP receptors, the linear V1 antagonist phenylacetyl-D-Tyr(Et)-Phe-Gln-Asn-Lys-Pro-Arg-NH2 (PhaaGln) displayed the greatest affinity [dissociation constant (Kd) = 0.05 +/- 0.01 nM]. The radioiodinated compound phenylacetyl-D-Tyr(Et)-Phe-Val-Asn-Lys-Pro-125I-labeled Tyr-NH2 (125I-labeled TyrPhaa) was characterized by a high affinity (Kd = 1.42 +/- 0.19 nM), a low nonspecific binding, and good stability. PhaaGln coupled to dodecabiotin retained a good affinity for V1-vascular AVP receptors (Kd = 1.41 +/- 0.20 nM). The complex PhaaGln-dodecabiotin-avidin is bifunctional, since an avidin-agarose column specifically bound V1-vascular AVP receptors labeled with 125I-TyrPhaa-dodecabiotin. In A7r5 vascular smooth muscle cells loaded with fura-2, PhaaGln and PhaaGln-dodecabiotin were pure antagonists as they blocked AVP-induced calcium mobilization but did not elicit a calcium signal by themselves. V1-vascular AVP receptors of A7r5 vascular smooth muscle cells were visualized by bound PhaaGln-dodecabiotin made fluorescent by labeling with fluorescein avidin. Thus linear V1-vascular AVP antagonists can be used as high affinity and specificity radioiodinated, biotinylated, and fluorescent probes to explore V1-vascular AVP receptors of human and animal origin.
authors.affiliation: Department of Medicine, University Hospitals of Cleveland, Ohio.
authors.forename: M
authors.initials: M
authors.lastname: Thibonnier
authors.forename: A L
authors.initials: AL
authors.lastname: Bayer
authors.forename: Z
authors.initials: Z
authors.lastname: Madhun
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001011:Aorta / Q000378:metabolism; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D001667:Binding, Competitive; D001710:Biotin; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005456:Fluorescent Dyes; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D051381:Rats; D017483:Receptors, Vasopressin / Q000187:drug effects / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D005456:Fluorescent Dyes; D007457:Iodine Radioisotopes; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D001710:Biotin; D002118:Calcium