Antibodies, albumin, and antimony: Comparison of three lymphoscintigraphic agents

The authors evaluated the kinetics of nodal and blood uptake of three lymphoscintigraphic agents: Tc-99m human serum albumin, Tc-99m antimony colloid, and I-125 5G6.4, a murine monoclonal antibody. Scanning doses of these agents were injected subcutaneous into the footpads of rats, or intravenously. Lymph nodes ipsilateral and contralateral to the subcutaneous injection site and blood (in the intravenously injected animals) were then sampled. Mean ipsilateral nodal uptakes (% kg-dose/g) at 1, 2, and 4 hours after the subcutaneous injection were as follows: for I-125 5G6.4, 4.07, 3.34, and 2.24; for Tc-99m hSA, 12.96, 9.51, and 9.33; and for Tc-99m antimony colloid, 114.5, 183.1, and 231.6. Uptake in ipsilateral and contralateral nodes after intravenous injection of these agents was near the background level. Ipsilateral nodal/blood ratios were 13.6, 72, and 1,900 for I-125 5G6.4, hSA, and antimony colloid, respectively. Thus, labeled antibodies have the least accumulation in lymph nodes after subcutaneous injection and antimony colloid has the highest accumulation, particularly at later time points. These data should be useful rationally planning lymphoscintigraphic studies