Abstract
This study was undertaken to examine the effect of bile salt on lymphatic absorption of vitamin D3 emulsified by milk fat globule membrane(MFGM) and to examine the mechanism of promotion of lymphatic drug absorption by MFGM. A soybean oil emulsion containing vitamin D3 which was prepared using MFGM as an emulsifier, was administered to rats. It was found that MFGM emulsion significantly enhanced lymphatic absorption of vitamin D3. The recovered percentage of vitamin D3 in lymph, administered in MFGM emulsion form, was 2.5 times higher than that in oil solution form. The percentage decreased to 1/32 when bile duct of the rat was fistulizated, and this recovered completely when taurocholate was infused in duodenum constantly. However, infusion of other surface active substance, such as tween 80, hardly increased lymphatic absorption of vitamin D3 in biliary fistula rats. MFGM emulsion, after diluted with taurocholate solution, tween 80 solution or water, was separated by ultracentrifugation. The fraction of microemulsion was collected and was administered to biliary fistula rats. Lymphatic absorption of vitamin D3 in the microemulsion with taurocholate was much greater than that in the microemulsion with tween 80 or with water. Furthermore, we confirmed that the ability of vitamin D3 transport to microemulsion by taurocholate was 2 times higher than that by tween 80 in vitro. These results suggest that promotion of lymphatic absorption of vitamin D3 by MFGM is partly due to the microemulsion formation in the presence of bile salt.
