INVESTIGATION OF MECHANISMS INFLUENCING THE ACCUMULATION OF ULTRASMALL SUPERPARAMAGNETIC IRON-OXIDE PARTICLES IN LYMPH-NODES

RATIONALE AND OBJECTIVES. The current study was designed to investigat e the lymph node accumulation mechanisms of dextran-coated ultrasmall superparamagnetic iron oxide particles (USPIO) in rats. METHODS. The i ron deposition in the lymph nodes after intravenous administration of USPIO at a dose of 200 mu mol Fe/kg was measured in vitro by inductive ly coupled plasma atomic emission spectrometer in control rats, in rat s after depletion of complement C3, after induction of antidextran ant ibodies, and with prior ligation of afferent lymphatic vessels, The re sults were correlated with baseline iron concentration and histology. RESULTS. A significant increase in iron concentration but unequal dist ribution between central and peripheral nodes occurred after administr ation of USPIO in rats, Much less accumulation was observed in guinea pigs. In rats, the nodal uptake of USPIO was not impaired by depletion of complement C3 using cobra venom factor, The central lymph nodes (m esenteric nodes) showed significantly more accumulation of iron partic les in the presence of antidextran antibodies induced by dextran preim munization, Afferent lymphatic vessel ligation did not effect iron par ticle accumulation. CONCLUSIONS. Accumulation of USPIO in lymph nodes is largely species-dependent but is independent of afferent lymphatic flow and of C3 complement opsonization in plasma, However, regional di stribution of particles can be influenced by preimmunization using dex tran.