The relation between the membrane cholesterol content and anion exchange in the erythrocytes of patients with cholestasis.

The anion transport system was assessed in erythrocytes from fifteen patients with cholestasis and fifteen healthy subjects as the exchange of intracellular chloride for extracellular pyruvate. The rate constant of pyruvate-chloride exchange was significantly reduced in the patients compared with the controls. The membranes of the erythrocytes of the patients compared with the controls contained more cholesterol and phospholipid and had a higher molar ratio of cholesterol to phospholipid. The rate constant of pyruvate-chloride exchange was directly related to the cholesterol to phospholipid ratio of the membranes in the patients. In vitro loading with cholesterol of erythrocytes from healthy subjects reduced the rate constant of pyruvate-chloride exchange by an amount which was related to the increase in the cholesterol to phospholipid ratio of the cell membrane. The inhibitory effect of cholesterol loading on anion transport was similar to its previously reported inhibitory effect on the furosemide-sensitive sodium transport system in the erythrocytes.