Correlation of cholesterol and bilirubin solubilization in bile salt solution.

Not only cholesterol but also bilirubin were considered to be solubilized by bile salt micelles. The correlation of cholesterol and bilirubin solubilization in aqueous conjugated and unconjugated bile salts solution and the effect of calcium on their solubilization were studied in this report. Cholesterol solubilization was usually reduced to some extent with increasing amount of added bilirubin. Bilirubin solubilization was always reduced by the co-existence of solubilized cholesterol. It was found that the addition of calcium increased cholesterol solubilization in conjugated bile salts system. On the other hand, calcium reduced bilirubin solubilization due to the formation of insoluble calcium bilirubinate especially in a high pH range of unconjugated bile salts system. Cholesterol solubilization in conjugated bile salts system was relatively lower than unconjugated bile salts system with or without added calcium, however co-existing bilirubin minimized these differences. The pH-dependency of cholesterol and bilirubin solubilization was small in conjugated bile salts system. On the contrary, it was remarkably bigger in unconjugated bile salts-calcium system.