Abstract
The regional differences in the capacities of absorption and lymphatic transport for lipid-soluble dyes, Sudan Blue and Oil Red XO, from oil-in-water emulsions were investigated in rat's whole gastrointestinal tract. The absorptive capacity was the highest in duodenum, followed by jejunum, ileum, large intestine, and the lowest in stomach. This was well compatible with the regional absorption of vehicle oil, triolein. Lymphatic transport of Sudan Blue was recognized only in duodenal and jejunal regions. This fact was supported by the observation of lymphatic staining, which also suggested the defect of usual lymphatic experiments dealed only the drained lymph fluids. It is also documented in this paper that lipid-soluble dyes are taken up into the intestinal epithelial cells from emulsions by an energy-independent process, since little or no inhibition was observed in various pretreated duodenum except the decrease of lymphatic transport in acetone washed intestine. However, severe damage in the villi was observed light microscopically when pretreated with high concentration (80%) of acetone, the absorption of Sudan Blue was significantly decreased in the case. These results suggest that the normality of macromorphological structure of mucosal surface is important for the absorption of lipid-soluble drugs from oil-in-water emulsions.
