Effect of bile salts on the hepatic regulation of serum lecithin: cholesterol acyltransferase activity

Abstract

The effect of bile salts on lecithin: cholesterol acyltransferase (LCAT) activity was studied in three groups of Wistar rats. Thirty percent increase of serum LCAT activity was observed in rats fed a 4% cholestyramine diet for 15 days which was accompanied by a simultaneous decrease of the serum esterified cholesterol concentration but the serum free cholesterol concentration remained unchanged. After bile duct ligation, the serum free cholesterol concentration increased progressively whereas the mean serum LCAT activities of three groups of rats killed 2, 6, and 8 hours after ligation were respectively 39, 51, and 140% of that of the sham-operated control rats. Eighty-two rats were used in 23 isolated liver perfusion studies including 10 “perfusions” performed without the liver in the circuit. These studies revealed a remarkable degree of non-enzymic degradation of the enzyme during perfusion. Perfusion of livers from rats previously fed a 4% cholestyramine diet resulted in a delay of the initial decline of perfusate LCAT activity associated with the maintenance of a steady state during the third and fourth hours of the perfusion. Such phenomena were abolished by addition of Na-taurocholate to the perfusate in a final concentration of 5 mg/dl which suggested a direct inhibitory effect of bile salts on the hepatic synthesis and release of LCAT.