Lipid solubilization in human gallbladder versus hepatic biles

Background/Aims: Cholesterol crystallizes more rapidly in gallbladder than in hepatic biles, supposedly due to formation of cholesterol-supersaturated vesicles in concentrated gallbladder biles because of preferential micelli zation of phospholipids compared to cholesterol. We therefore aimed to comp are lipid solubilization in hepatic and gallbladder biles. Methods: Mixed micellar and vesicular phases were separated from hepatic an d associated gallbladder biles of seven cholesterol gallstone patients by u sing state-of-the-art gel filtration with bile salts at intermixed micellar /intervesicular compositions and concentrations in the eluant. Results: Vesicles mere found in 6 out of 7 hepatic biles, but only in 2 of the corresponding gallbladder biles. Both percentage (7.8+/-5.1 vs. 36.3+/- 7.6%; p=0.01) and amount (0.9+/-0.2 vs. 1.7+/-0.3 mM; p=0.06) of vesicular cholesterol were lower in gallbladder biles. Similar results were found for vesicular phospholipids (1.3+/-0.8 vs. 11.6+/-6.0%; p=0.05; and 0.3+/-0.1 vs. 1.1+/-0.5 mM; p=0.07), The vesicular cholesterol/phospholipid ratio was 1.7+/-0.5 in hepatic bile but 4.3 and 1.8 in the 2 gallbladder biles which contained vesicles. Mixed micelles in gallbladder biles had a higher chole sterol saturation index than mixed micelles in hepatic biles (1.43+/-0.11 v s. 1.15+/-0.07; p=0.02). Conclusions: Concentration of bile in the gallbladder leads to decreased ve sicular lipid contents. The finding of supersaturated mixed micelles in the absence of vesicles in a significant number of patients points to the poss ibility of non-vesicular modes of crystallization.