Experiments on the transport of cholesterol, desmosterol and hydroxychole- sterol from aqueous sodium taurocholate-lecithin and aqueous sodium cholate-

Experiments on the transport of cholesterol, desmosterol and hydroxycholesterol from aqueous sodium taurocholate-lecithin and aqueous sodium cholatelecithin micelle systems into hexadecane have been carried out as a function of lecithin to bile salt concentration ratios. These data strongly support the previously proposed hypothesis that the kinetics of transport of cholesterol, desmosterol and hydroxycholesterol is (I) interfacially controlled and C2) involves a two-step process in which there is first a collision of the solute-mlcelle complex with the oil-water interface and this is followed by the release of the solute from the micelle in a largely polar environment at the interface. The experimental evidence for this mechanism is that (I) effective interfacial barrier permeability coefficients for sterol transport has been found to be independent of bile salt-lecithin concentrations, when the ratio of lecithin to the bile salt was kept constant, and (2) when the lecithin-bile salt ratio was increased, keeping the bile salt concentration constant, it was found that the interfacial barrier permeability coefficients for the sterols decreased.