title: Comparative properties of a technetium-99m-labeled single-stranded natural DNA and a phosphorothioate derivative in vitro and in mice.
abstract: Oligonucleotides, particularly single stranded, may ultimately be of considerable use as radiopharmaceuticals. We have compared a synthetic 22-base single-stranded phosphodiester DNA with its phosphorothioate analog after both were radiolabeled with 99mTc via the hydrazino nicotinamide chelator. Whole body clearance of the label in mice was much slower when introduced on the phosphorothioate (30% vs. 75% clearance at 6 hr) because of immediate and persistent accumulation in liver (47% vs. 2% injected dose/g at 4 hr). The label in both cases was present in urine primarily on low molecular weight catabolites. High-performance liquid chromatography analysis of 37 degrees C serum incubates showed serum protein binding of 99mTc in both cases (about 100% bound at 24 hr) but to different proteins. Different behavior with respect to protein binding was also observed in the analysis of liver and kidney homogenates: the phosphodiester label was almost quantitatively converted to lower molecular weight catabolites after only 15 min, whereas the phosphorothioate label was primarily on proteins. The rapid digestion of the phosphodiester by nucleases was not observed, probably because protein binding of the labeled oligonucleotides stabilized against degradation. Thus the phosphodiester DNA may be the preferred 99mTc-labeled oligonucleotide in certain circumstances to avoid the high and persistent liver uptake observed with the phosphorothioate DNA.
authors.affiliation: Department of Nuclear Medicine, University of Massachusetts Medical Center, Worcester, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Hnatowich
authors.forename: G
authors.initials: G
authors.lastname: Mardirossian
authors.forename: M
authors.initials: M
authors.lastname: Fogarasi
authors.forename: T
authors.initials: T
authors.lastname: Sano
authors.forename: C L
authors.initials: CL
authors.lastname: Smith
authors.forename: C R
authors.initials: CR
authors.lastname: Cantor
authors.forename: M
authors.initials: M
authors.lastname: Rusckowski
authors.forename: P
authors.initials: P
authors.lastname: Winnard
mesh_terms: D000818:Animals; D001483:Base Sequence; D001710:Biotin / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D004277:DNA, Single-Stranded / Q000138:chemical synthesis* / Q000493:pharmacokinetics*; D007553:Isotope Labeling / Q000379:methods; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000138:chemical synthesis / Q000493:pharmacokinetics; D015609:Organotechnetium Compounds / Q000138:chemical synthesis* / Q000493:pharmacokinetics*; D013873:Thionucleotides / Q000138:chemical synthesis* / Q000493:pharmacokinetics*; D014018:Tissue Distribution
chemical_list: D004277:DNA, Single-Stranded; D009841:Oligonucleotides; D015609:Organotechnetium Compounds; D013873:Thionucleotides; D001710:Biotin