title: Design, synthesis and pharmacological characterization of new highly selective CRF(2) antagonists: development of 123I-K31440 as a potential SPECT ligand.
abstract: Novel analogs of antisauvagine-30 (aSvg-30), a specific antagonist for corticotropin-releasing factor (CRF) receptor, type 2 (CRF(2)), have been synthesized and characterized in vitro and in vivo. The N-terminal amino acid D-phenylalanine in aSvg-30 was replaced by a D-tyrosine residue for specific radioactive labeling with 123I. Additionally, Met(17) of aSvg-30 was substituted by norleucine and the N-terminus of the peptide was acetylated to increase in vivo metabolic stability. The aSvg-30 analogs were tested for their ability to displace [125I-Tyr(0)]Svg in binding experiments and to inhibit Svg-stimulated adenylate cyclase activity in human embryonic kidney (HEK) 293 cells, permanently transfected with cDNA coding for the human CRF(1) (hCRF(1)), hCRF(2alpha) and hCRF(2beta) receptor. Ac-[D-Tyr(11), His(12), Nle(17)Svg(11-40), named K31440, showed high specific binding to hCRF(2alpha) (K(i) = 1.48 +/- 0.34 nM) and hCRF(2beta) (K(i) = 2.05 +/- 0.61 nM) but not the hCRF(1) receptor (K(i) = 288 +/- 13 nM) and decreased Svg-stimulated cAMP activity in hCRF(2)-expressing cells in a similar fashion as aSvg-30. In biodistribution studies specific uptake of 123I-K31440 was detected after 1 h in small intestine of BALB/c nude mice. These data demonstrate that 123I-K31440 may serve as a useful tool to detect native CRF(2) receptors and elucidate their role in gastrointestinal disorders and diseases such as irritable bowel syndrome or cancer.
authors.affiliation: Radiopharmaceuticals Division, Australian Nuclear Science & Technology Organisation, NSW 2234, Menai, Australia. arx@ansto.gov.au
authors.forename: A
authors.initials: A
authors.lastname: Rühmann
authors.forename: J
authors.initials: J
authors.lastname: Chapman
authors.forename: J
authors.initials: J
authors.lastname: Higelin
authors.forename: B
authors.initials: B
authors.lastname: Butscha
authors.forename: F M
authors.initials: FM
authors.lastname: Dautzenberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D015195:Drug Design; D004355:Drug Stability; D006801:Humans; D007457:Iodine Radioisotopes / Q000737:chemistry; D008024:Ligands; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D023421:Models, Animal; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D018019:Receptors, Corticotropin-Releasing Hormone / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
chemical_list: C451508:123I-K31440 peptide; C101531:CRF receptor type 2; D007457:Iodine Radioisotopes; D008024:Ligands; D010455:Peptides; D019275:Radiopharmaceuticals; D018019:Receptors, Corticotropin-Releasing Hormone; D000242:Cyclic AMP