The Effect of Free Fatty Acids, Bile Acids, and Hematin on Bilirubin Binding by Human Erythrocytes

Abstract

The effect of free fatty acids (FFA), bile acids, and hematin on bilirubin binding by erythrocytes was investigated by adding increasing concentrations of these substances to incubation mixtures of bilirubin, albumin, and erythrocytes. It was found that both cholic acid and taurocholic acid increased the cellular binding of bilirubin. With bilirubin/albumin ratios below unity this effect was greatly potentiated by reducing the pH from 7.4 to 7.0–6.8. Hematin also increased the cellular binding of bilirubin; this effect seemed not to be potentiated by reduction in pH. With bilirubin/albumin ratios below unity, oleate was also found to increase cellular binding of bilirubin when the molar FFA/albumin ratio exceeded 6. With bilirubin/albumin ratios above unity, however, increased amounts of FFA reduced the cellular binding of bilirubin, especially at low pH. The findings and their possible clinical significance are discussed.