TRANSPORT BEHAVIOR OF 4 BILE-SALT MICELLES AND CHOLESTEROL SOLUBILIZED BY THEIR MICELLES ACROSS POROUS MEMBRANE

The transport behavior of bile salts (BSs) solubilizing cholesterol (C h) or none across an artificial membrane was investigated for sodium s alts of deoxycholic acid (NaDC), chenodeoxycholic acid (NaCDC), ursode oxycholic acid (NaUDC) and cholic acid (NaC) in tetraborate-carbonate buffer solution at pH 10.0 and 37 degrees C. The study demonstrated th at the surfactant properties such as critical micellization concentrat ion (CMC) and micellar size or diffusion coefficient were determinable from the flux or permeability measurements. The comparison among the respective pure systems of BSs led to a conclusion that the micellar s ize was in the order of NaDC > NaCDC > NaUDC > NaC and determined CMC values were in agreement with those in literature. The magnitude of so lubilizing power (capacity) of BS for Ch was found to decrease in the order of NaDC > NaCDC > NaC > NaUDC; this order is in accordance with that of the empirical hydrophobicity index. The hydrodynamic radii for the singly dispersed species and the micellar species of the respecti ve BSs and of Ch-solubilizing micelles were estimated from the permeab ility data; the radii of the Ch-solubilizing micelles are approximatel y 12-15 Angstrom and interestingly, smaller than those of the respecti ve BS alone micelles ranging from 14 to 22 Angstrom.