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 the body remains a controversial issue of relevance in various fields of study. In this report fluorescent polystyrene latex microparticles in the size range of 2 microns were used as models for nonspecifically absorbed nonbiodegradable particulates. They were administered to young adult rats as a single oral dose of 1.65 x 10(9) particles; Peyer's patches and surrounding normal absorptive small intestinal tissue were collected at various time points. Quantification of solubilized tissue samples and fluorescence (epi- and confocal) qualitative and quantitative microscopy showed uptake of latex microparticles in all parts of the intestine sampled, but with the proximal segment the preferential site of absorption. The maximum uptake of particles occurred 0.5 hr after dosing in all three segments of the small intestine; there were progressively 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 occurred 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 provide new information regarding site- and time-related effects on particle uptake and the involvement of the villous epithelium in particle translocation.