The electrophoretic mobility of lipoprotein X in postheparin plasma

After incubation whole plasma and low density lipoproteins (LDL) taken before and 10 min after intravenous administration of heparin, from a patient with primary biliary cirrhosis and a patient with familial lecithin:cholesterol acyltransferase (LCAT) deficiency, have been tested for the presence of lipoprotein X (LP-X) by agar gel electrophoresis. LP-X was present in preheparin whole plasma and LDL. No precipitation lines on the cathodal side of the wells, indicating the absence of LP-X, were seen after electrophoresis of postheparin plasma and LDL. Immunodiffusion revealed the presence of apo-beta-lipoproteins and LP-X in preheparin as well as postheparin LDL. After gel filtration three subfractions and similar patterns were observed in the preheparin and postheparin LDL. Electronmicroscopical examination of the intermediate subfractions showed LP-X-like particles in preheparin and postheparin samples. These observations indicate a changed electrophoretic mobility in agar gel of postheparin LP-X, giving a false negative LP-X test by the conventional agar gel electrophoresis.