Fibronectin in human gallbladder bile: cholesterol pronucleating and/or mucin "link" protein?

Some biliary proteins (pronucleators) seem to be essential factors
for cholesterol crystal formation and crystal growth in bile. A
recent study suggests that fibronectin is such a pronucleator in
bile. Fibronectin also seems to closely interact with intestinal
mucin. Since biliary mucin plays an important role in gallstone
formation, such an interaction in bile may be of relevance in
cholesterol gallstone formation. To more clearly elucidate the role
of fibronectin in cholesterol gallstone disease, we measured the
concentration of fibronectin in native bile of cholesterol
gallstone patients and checked its influence on the cholesterol
nucleation time of model bile. We further looked for a molecular
interaction between biliary fibronectin and gallbladder mucin. We
found that fibronectin is present in gallbladder bile of gallstone
patients in low concentrations (2.6 +/- 1.2 micrograms/ml). Bile
fibronectin did not interact with gallbladder mucin. Moreover, in a
wide range of concentrations fibronectin had no influence on the
nucleation time of model bile. We conclude that fibronectin does
not seem to play a major role in cholesterol gallstone disease.