Abstract
Colloidal particles are widely used as tracer and vehicle of drugs which target the lymph nodes. Little information, however, exists regarding mechanisms of colloidal accumulation in the lymph nodes in vivo. Thus, in this study, we have attempted to evaluate size-dependent mechanisms for accumulation of colloidal particles in the lymph nodes in vivo. Male Japan White rabbits were anesthetized with ketamine (20 mg/kg iv.) and pentobarbital (20 mg/kg iv.). Centripetal and retrograde cannulations were performed in one of the popliteal afferent and efferent lymph vessels, respectively. All other efferent lymphatics were ligated completely. Labeled latex with fluorescence microspheres with 0.5, 1.1, 1.7 and 1.9 μm in diameter were injected into the afferent lymph vessel. Two microgram of each particle was administered at one time and artificial lymph fluid was injected through the same route at constant rate of 1.47 ml/h. Then, changes in concentration of the microspheres in the efferent lymph vessel were determined by measuring the number of the particles under a fluorescent microscope. 11.0 ± 6.4% of the 0.5 μm-microsphere passed through the lymph node in 2.5 h. On the other hand, no microsphere with 1.9 μm in diameter was observed in the efferent lymph. The decreasing order of ability for accumulating in the lymph node was as follows: 1.9 μm > 1.7 μm >1.1 μm > 0.5 μm-microsphere. These results strongly suggest that size-dependent accumulating mechanisms exist in the lymph node. [J Physiol Sci. 2006;56 Suppl:S131]
