The significance of vehicle oil metabolism in the absorption process of lipid-soluble compounds.

The significance of vehicle oil metabolism in the absorption of lipid-soluble compounds from oil-in-water emulsions was investigated in rat small intestine using lipidsoluble dyes, Sudan Blue and Oil Red XO, and vitamin A acetate as model compounds. Although little difference was observed among their initial uptake rates, negligible amount of lipid-soluble compounds was absorbed from oleic acid emulsions during the first hour whereas an obvious amount of them was absorbed from triolein emulsions. From oleic acid-triolein mixed emulsions their absorption were decreased as oleic acid-triolein ratio was increased. These results suggested that in the presence of oleic acid lipid-soluble compounds were pooled in some components of epithelial cells. This was well supported by the distribution experiments of Sudan Blue and Oil Red OX into the brush border fraction of the epithelial cells. In the case of oleic acid emulsions, about three to five times as much of dyes were bound to the brush border fraction as compared with triolein emulsions. This phenomenon was considered to be the reflection of the affinity of lipid-soluble compounds to oils, which was partly indicated by the solubilities of the former in the later. It seems probable that the saturation of absorption of lipid-soluble dyes from triolein emulsions, described in our previous paper, is mainly due to the strong affinity of dyes to the membrane components in the presence of oleic acid which was produced from the hydrolysis of triolein.