UPTAKE AND TRANSLOCATION OF MICROPARTICLES IN SMALL-INTESTINE - MORPHOLOGY AND QUANTIFICATION OF PARTICLE DISTRIBUTION

The intestinal transit of large (micro-) particles to other sites of t he body remains a controversial issue of relevance in various fields o f study. Ia this report fluorescent polystyrene latex microparticles i n the size range of 2 mu m were used as models for nonspecifically abs orbed nonbiodegradable particulates. They were administered to young a dult rats as a single oral dose of 1.65 x 10(9) particles; Peyer's pat ches and surrounding normal absorptive small intestinal tissue were co llected at various time points. Quantification of solubilized tissue s amples and fluorescence (epi- and confocal) qualitative and quantitati ve microscopy showed uptake of latex microparticles in all parts of th e intestine sampled, but with the proximal segment the preferential si te of absorption. The maximum uptake of particles occurred 0.5 hr afte r dosing in all three segments of the small intestine; there were prog ressively smaller numbers with distance from the pylorus and with time . Translocation of small numbers of particles to the mesenteric lymph nodes was also detected at 0.5 hr. Transmucosal passage of particles o ccurred primarily in the villous tissues adjacent to the Peyer's patch regions. These studies give confirmatory evidence for the uptake and translocation of microparticulates across the mucosal barrier and prov ide new information regarding site- and time-related effects on partic le uptake and the involvement of the villous epithelium in particle tr anslocation.