Serum lecithin: cholesterol acyltransferase activity in the bile duct-ligated rat.

Serum lipoprotein cholesterol concentration, lecithin: cholesterol acyltransferase (LCAT) activity and lipoprotein X (LP-X) were studied after acute cholestasis had been produced by ligation of the common bile duct in rats fed a liquid fat-free diet. The concentration of serum-free cholesterol, predominantly contained in the low density lipoprotein fraction, increased steadily up to 72 h after ligation. The concentration of cholesterol in the high density lipoprotein fraction did not change significantly, and similarly the serum concentration of esterified cholesterol was not altered. The activity of LCAT, expressed in molar terms as millimoles of cholesterol esterified per litre per hour, did not change during the 72-hour study period. These data indicate acute cholestasis in the rat does not result in a LCAT deficiency and suggest that the accumulation of serum-free cholesterol in this situation is independent of the serum cholesterol-esterifying mechanism.