title: Synthesis and biological evaluation of Tc-99m-cyclopentadienyltricarbonyltechnetium-labeled octreotide.
abstract: Octreotide was labeled at its N-terminus with Tc-99m-cyclopentadienyltricarbonyltechnetium, and the biodistribution of the labeled conjugate was studied in adult female Sprague-Dawley rats. The synthesis began with the preparation of Tc-99m-(methoxycarbonylcyclopentadienyl) tricarbonyltechnetium from Tc-99m-pertechnetate using a novel double ligand transfer reaction; it was completed in a total of five steps, with an 8% overall radiochemical yield (15% decay-corrected). The 99mTc-cyclopentadienyltricarbonyltechnetium-labeled octreotide conjugate (99mTc-CpTT-octreotide) showed receptor-mediated uptake in the pancreas and adrenals, which was blocked (80% and 93%, respectively) by excess unlabeled octreotide. These studies illustrate a new method for labeling a peptide with Tc-99m through an organometallic linkage that is stable, nonpolar, and low molecular weight; it complements labeling approaches that utilize inorganic metal complexes.
authors: Department of Chemistry, University of Illinois, Urbana 61801, USA.
authors: T W
authors: TW
authors: Spradau
authors: W B
authors: WB
authors: Edwards
authors: C J
authors: CJ
authors: Anderson
authors: M J
authors: MJ
authors: Welch
authors: J A
authors: JA
authors: Katzenellenbogen
mesh_terms: D000311:Adrenal Glands / Q000378:metabolism*; D000818:Animals; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007553:Isotope Labeling; D008024:Ligands; D008099:Liver / Q000378:metabolism; D015282:Octreotide / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology; D009928:Organ Specificity; D015609:Organotechnetium Compounds / Q000138:chemical synthesis* / Q000378:metabolism / Q000493:pharmacokinetics; D010179:Pancreas / Q000378:metabolism*; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000378:metabolism / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D017481:Receptors, Somatostatin / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D008024:Ligands; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; C120319:technetium Tc 99m cyclopentadienyltricarbonyloctreotide; D015282:Octreotide