The effect of sodium oleate on cholesterol solubility in bile salt-lecithin model systems.

Abstract

Reflux of pancreatic secretions and bacterial infection have been suggested as important factors in gallstone formation in some instances by introducing into bile phospholipases hydrolyzing lecithin to lysolecithin, mono- and diglycerides, and free fatty acids. Since there is little data on free fatty acids, we studied the effect of sodium oleate, the soap of one of the major fatty acid derivatives of lecithin, on cholesterol solubility in unconjugated bile salt-lecithin model solutions to see if an increase in this component might lead to saturation of bile with cholesterol. In the absence of lecithin, sodium oleate decreased cholesterol solubility in bile salt solutions at concentrations physiologic for bile, although cholesterol solubility was increased by oleate at higher oleate-bile salt ratios. In the presence of lecithin, sodium oleate decreased cholesterol solubility at all concentrations studied. Significant differences in cholesterol solubility were found for all comparable concentrations of sodium cholate and deoxycholate studied, both in the presence and absence of lecithin. Our studies showed that an increase in free fatty acid concentration can increase cholesterol saturation significantly in unconjugated bile salt-lecithin model solutions. Whether or not free fatty acid concentrations in pathologic bile reach levels sufficient to contribute to cholesterol saturation and gallstone formation cannot be determined until more adequate data on the minor lipid composition of bile becomes available.