EFFECTS OF BILE-SALT HYDROPHOBICITY ON CRYSTALLIZATION OF CHOLESTEROLIN MODEL BILE

Precipitation of cholesterol crystals is an essential step in gallston e formation. In the present study we found much faster and more extens ive precipitation of various cholesterol crystal shapes in whole model biles containing the hydrophobic bile salt taurodeoxycholate than in biles containing the relatively hydrophilic taurocholate. Addition of taurodeoxycholate to isolated cholesterol-phospholipid vesicles also i nduced more crystallization than taurocholate. Crystallization behavio ur in whole model biles and in vesicles after addition of correspondin g bile salts was very similar. The very hydrophilic bile salts taurour sodeoxycholate and taurohyodeoxycholate never induced crystallization from vesicles, and crystallization in corresponding whole model biles did not occur. These bile salts also reduced crystallization dose depe ndently after addition of taurodeoxycholate to vesicles. Ultracentrifu gation experiments suggested a higher vesicular cholesterol-phospholip id ratio for whole model biles containing more hydrophobic bile salts. These findings indicate that bile salt hydrophobicity influences shap e of cholesterol crystals and extent of crystallization, possibly by m odulating the vesicular cholesterol-phospholipid ratio.