AJP - Endocrinology and Metabolism, Vol 265, Issue 6 E906-E913, Copyright © 1993 by American Physiological Society

ARTICLES

Linear V1-vascular vasopressin antagonists suitable for radioiodination, biotinylation, and fluorescent labeling

M. Thibonnier, A. L. Bayer and Z. Madhun
Department of Medicine, University Hospitals of Cleveland, Ohio.

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.

This article has been cited by other articles:

				G. Innamorati, H. Sadeghi, and M. Birnbaumer Transient Phosphorylation of the V1a Vasopressin Receptor J. Biol. Chem., March 20, 1998; 273(12): 7155 - 7161. [Abstract] [Full Text] [PDF]

				Z. Strakova, A. Kumar, A. J. Watson, and M. S. Soloff A New Linear V1A Vasopressin Antagonist and Its Use in Characterizing Receptor/G Protein Interactions Mol. Pharmacol., February 1, 1997; 51(2): 217 - 224. [Abstract] [Full Text] [PDF]