Large unilamellar vesicles were prepared from phosphatidylcholine (PC), sph
ingomyelin (SM), cholesterol (Chol) and cardiolipin (CL) by an extrusion te
chnique (LUVETs). Diffusion of the more hydrophobic lithocholic acid (LCA)
and the less hydrophobic chenodeoxycholic acid (CDCA) was investigated by u
sing the pyranine fluorescence method. Membrane permeability was studied by
measuring the inclusion of carboxyfluoresceine (CF) into the lipid vesicle
s, and membrane fluidity was determined with diphenylhexatriene (DPH) and t
rimethylammonium-diphenylhexatriene (TMA-DPH). All results indicate that, C
DCA compared to LCA, exhibits a significantly better penetration into vesic
les containing SM. LCA penetrates better into vesicles containing cholester
ol. Small amounts of CL influenced the diffusional properties of CDCA more
than those of LCA. Since Lamcharfi et al. (1997a) Euro. Biophys. 25, 285-29
1 have observed differences in the conformational forms of CDCA and LCA in
solution, it is suggested that the diffusion rate of bile acids through (mo
del-)membranes is not only dependent on hydrophobicity, but also on bile ac
id di-(poly-)meric associations and on membrane-lipid composition. (C) 2001
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