Enhancement of Membrane Permeability to a Poorly Absorbed Drug by Medium-Chain Glycerides: Effect of Medium-Chain Glycerides on the Release of Phenol Red from Egg Phosphatidylcholine Liposomes

The influence of medium-chain glyceride (MCG) on the membrane permeability was in-vestigated. Liposomes with a basal composition of egg phosphatidylcholine: cholesterol = 4:1 were used to examine the effect of MCG and its components on the release of phenol red (PR) through the liposomal membrane by the dynamic dialysis method. With increase of MCG content in the membrane, the release of PR was enhanced. Among MCG components tested, dicaprylglyceride and tricaprylglyceride enhanced the release. When MCG emulsion was added to the control liposome suspension, PR was released more rapidly than from liposome without addition of MCG emulsion. To investigate the mechanism of the enhancement of membrane permeability, the effect of temperature on the release of PR was examined. The activation energies calculated from the slope of Arrhenius plots did not change significantly with the addition of MCG, so that it was unclear whether the change of membrane permeability could be correlated with the membrane fluidity.