Effect of medium-chain glycerides on the intestinal absorption and the hepatobiliary transport of Phenol red

The effects of medium-chain glyceride (MGK) on the intestinal absorption and the hepatobiliary transport of Phenol red (PR) were investigated in rats. The in situ recirculation experiment using the small intestine showed that disappearance of PR from the recirculated MGK emulsion at a lipid content of 4% was over 5 times greater than that from the buffer solution, although the effect diminished with the increase of the lipid content. On the contrary, in the everted sac experiments, mucosal to serosal transport of PR from MGK emulsion was reduced to about one half of the control, and the pretreatment with PR-free MGK emulsion could not enhance PR disappearance from the buffer solution recirculated successively. The effect of a polyoxyethylene derivative of castor oil (HCO-100) employed for emulsion preparation on the transport of PR was investigated by the everted sac experiments. The amount of PR transported was decreased with the increase of HCO-100 in the range of 0.1-2.0%. These results may suggest that other factors are related with the promoting effect except for the membrane permeability. When the absorption of MGK components was examined by in situ and in vitro studies, the disappearance of MGK components in the former was nearly twice of that in the latter. The inhibiting effect of MGK on the biliary excretion of PR was observed in the in situ recirculation study with MGK emulsion containing PR. The biliary excretion percent of PR was also significantly reduced by injecting the components of MGK into the mesenteric vein.