Lipoproteins in plasma from patients with low LCAT activity due to biliary obstruction.

A high density lipoprotein (HDL) fraction, designated cholestatic HDL1, has been isolated by zonal ultracentrifugation from patients with long-standing biliary obstruction. This lipoprotein fraction consists exclusively of disc-shaped particles rich in phospholipid and unesterified cholesterol. The fatty acid composition of the minor cholesteryl ester fraction was characterized by a low content of linoleic acid. Apoprotein E was the dominating protein' component, while only small amounts of apolipoprotein A-I were found. Immunochemical studies of cholestatic HDL1 indicate that a considerable proportion of the particles contained apo E as its only protein constituent. All patients had a markedly reduced endogenous cholesterol-esterifying ability. The finding of apparently primary LpE particles in biliary obstruction may be related to this secondary LCAT deficiency.