抄録
Micro- and nano-particles are known to be taken up into initial lymphatics. The particles have been used for efficient delivery of drugs and diagnostic agents to lymphatic system. Little information, however, exists regarding size-dependent mechanisms for the particle uptake. Thus, in this study, we have attempted to evaluate effects of size on uptake of the particles. Male Japan White rabbits were anesthetized with ketamine chloride (20 mg/kg iv.) and pentobarbital sodium (20 mg/kg iv.). Retrograde cannulation was performed in one of the popliteal afferent lymph vessels. Labeled latex with fluorescence microspheres with 0.5, 1.1, 2.0, 5.6 and 10.0 μm in diameter were injected subcutaneously at dorsal portion of rabbit foot. Then, concentrations of the microspheres in the efferent lymph vessel were determined by measuring the number of the particles under a fluorescent microscope. The decreasing order of particle concentration in efferent lymph was as follows: 0.5 μm > 1.1 μm > 2.0 μm-particle. No particle with 5.6 and 10.0 μm in diameter was observed in the efferent lymph. When mechanical massage was administered on the injection site, both lymph flow rate and particle concentration were markedly increased. These results strongly suggest that size- and mechanical stimulation-dependent mechanisms exist in transport of micro- and nano-particles from subcutaneous tissue into the lymphatic system. [J Physiol Sci. 2006;56 Suppl:S132]
