Changes in the concentration of lipoprotein-X during incubation of postheparin plasma from patients with familial lecithin: cholesterol acyltransferase (LCAT) deficiency.

The concentration of lipoprotein-X (LP-X) has been studied in six patients with familial lecithin:cholesterol acyltransferase (LCAT) deficiency before and after the administration of heparin. In preheparin plasma, LP-X was present in all the patients, the concentrations ranging from 40 to 251 mg/100 ml. When postheparin plasma samples were incubated at 37 degrees C for 4 hours, LP-X could not be detected, whereas it was still present before incubation. LCAT activity was absent in the preheparin as well as in the postheparin samples. Accordingly, the changes in the concentration of LP-X could not be attributed to alterations in plasma LCAT activity. An increase in lysolecithin and a decrease in lecithin was observed during incubation of postheparin plasma samples.