title: Optimal 99mTc radiolabeling and uptake of glucosamine sulfate by cartilage. A potential tracer for scintigraphic detection of osteoarthritis.
abstract: Glucosamine sulfate (GS) is used in treatment of human osteoarthritis, but no data for(99m)TcGS scintigraphy are available. Radiolabeling of GS was performed using the (99m)TcO(4)(-)/tin method. We applied two procedures for separation of free (99m)Tc using PD10 and G10 columns. In each eluted fraction, GS content was estimated by the Elson/Morgan method. For optimal radiolabeling, we varied the amount of GS, tin, (99m)Tc activity, and pH. For uptake age matched human rib cartilage (males, 78 and 63 years old) and 5-10 μCi/well of (99m)TcGS were used. Uptake was monitored up to 72 h. Also, washout of the tracer 3 h and 24 h after uptake was investigated. At pH 2, using PD10 column, the uptake of (99m)TcGS amounted to 100.8 ± 2.9%, n = 6 at saturation time of 72 h. Uptake was age-dependent; at pH 5, it amounted to 99.8% as compared to 66.1% at 78 vs 63 years old. When the amount of tin was varied at pH 2, the tracer uptake amounted to 21.37% (1 mg) vs 45.99% (2.5 mg) at saturation. At pH 7, the amount of needed tin was much lower and amounted to 42.50 ± 2.50% using 0.1 mg vs 25.11 ± 1.90% using 0.05 mg. Although the uptake at pH 7 (0.1 mg tin) is comparable with that at pH 2 (2.5 mg tin), the washout of the tracer amounted only to 4.10 ± 1.25% and 2.05 ± 0.65% after 3 h and 24 h, respectively. During degeneration of cartilage, incorporation of (99m)TcGS is high and could therefore be a promising tracer not only to target osteoarthritis but also to monitor the effects of therapy.
authors.affiliation: University Clinic of Nuclear Medicine, Department of Nuclear Medicine, Medical University of Vienna, Vienna, Austria. Grazyna.Sobal@meduniwien.ac.at
authors.forename: Grazyna
authors.initials: G
authors.lastname: Sobal
authors.forename: Johannes
authors.initials: J
authors.lastname: Menzel
authors.forename: Helmut
authors.initials: H
authors.lastname: Sinzinger
mesh_terms: D000368:Aged; D002356:Cartilage / Q000378:metabolism*; D005944:Glucosamine / Q000737:chemistry / Q000493:pharmacokinetics*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007553:Isotope Labeling; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000378:metabolism*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012272:Ribs; D013667:Technetium / Q000737:chemistry / Q000493:pharmacokinetics; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D019275:Radiopharmaceuticals; D013667:Technetium; D005944:Glucosamine