Abnormal lipoprotein appearing in plasma of patients who received a ten percent soybean oil emulsion infusion.

: In 42 of 43 surgical patients who received a 10% soybeam oil emulsion (Intralipid), abnormal lipoprotein was detected in their plasma 1 to 2 days after the initial Intralipid infusion. This abnormal lipoprotein was proven to appear as a result of the infusion of soybean oil emulsion regardless of the patient's original diseases, age, sex, liver function, or concomitantly administered solutions. In addition, this abnormal -ipoprotein was found to have various similarities to lipoprotein-X (LP-X) which is found in plasma from patients with obstructive jaundice or familial lecithin:cholesterol acyltransferase deficiency. Therefore, this abnormal lipoprotein was tentatively named LP-X--like substance (LP-X-LS). A comparison of the properties of LP-X and LP-X-LS was performed and the following results were obtained: (1) LP-X-LS migrated toward the cathode on Bacto-Agar gel electrophoresis similarly to LP-X; (2) the stability of LP-X and LP-X-LS against heating and freezing were almost equal under various conditions; (3) LP-X-LS could be absorbed by anti--LP-X serum; (4) LP-X-LS existed in low density fraction (d = 1.063) separated by ultracentrifugation from plasma; (5) electron microscopic study of low-density lipoprotein particles from LP-X-LS positive plasma revealed that LP-X-LS had a similar ultrastructure to LP-X. From these results it is suggested that LP-X-LS is an abnormal lipoprotein quite similar to LP-X.