title: Labeling of polypeptides with technetium-99m using a dextran spacer.
abstract: Radioimmunoscintigraphy and other forms of scintigraphy are becoming increasingly important as tools in detection and evaluation of cancer diseases. Several radionuclides can be considered as radiolabel; however, 99mTc may be the most suitable because of easy availability and near ideal physical properties. This study describes how dextran is coupled to a monoclonal anticytokeratin antibody, epidermal growth factor, and somatostatin through stable amine bonds. The dextran moiety could then be labeled with 40-62 MBq of 99mTc. The labeling efficiency was 60-94%, determined by gel filtration or TLC. The specific binding could be considerably preserved after the dextranation, the antibody retained > 90% of its activity, epidermal growth factor bound with > 90% specificity to receptor-expressing tumor cells, and somatostatin showed approximately 40% specific binding to rat adrenal homogenates. Because somatostatin only has a transient half-like in vivo, the in vivo plasma half-life of somatostatin-dextran was tested in normal female Sprague-Dawley rats. The result showed a strong enhancement of the plasma half-life that was dependent on two compartments, 4 and 8 h.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000276:immunology; D003911:Dextrans; D004815:Epidermal Growth Factor / Q000737:chemistry*; D005260:Female; D006207:Half-Life; D007553:Isotope Labeling; D007633:Keratins / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013004:Somatostatin / Q000737:chemistry* / Q000276:immunology / Q000493:pharmacokinetics; D013667:Technetium / Q000737:chemistry*
chemical_list: D000911:Antibodies, Monoclonal; D003911:Dextrans; D013004:Somatostatin; D004815:Epidermal Growth Factor; D007633:Keratins; D013667:Technetium