MATERIALS AND METHODS The human apolipoproteins E, CI, C-11, and C-111-2’were all prepared from normal humans or patients with hyper pre-P lipoproteinemia (Type IV) by previously published methodology (4-6). The purity of the preparation was defined by polyacrylamide gel electrophoresis in both a sodium dodecyl sulfate (7) and urea (8) buffer. Antisera to these human apoproteins prepared in the rabbit were also used to define purity.

Triglyceride emulsions for these studies were prepared as previously described (1). Triolein, egg phosphatidylcholine, and cholesterol in a 5: 2: 1 mixture by weight were dried down from benzene. The dried lipid was rehydrated with Krebs-Ringer bicarbonate buffer and sonicated using a Branson sonifier (Danbury, CT) at 75 watts for 3-min intervals for a total of 12 min at 4 “C under nitrogen. Three parts of the sonicated emulsion were mixed with one part Liposyn (Abbott Labs, IL), a commercially prepared triglyceride emulsion obtained from safflower oil, and the mixture spun at 25,000 rpm for 20 min at 4 “C in a 40 rotor using a Beckman L5-65 ultracent. rifuge (Palo Alto, CA). The mulsions were radiolabeled with either VHIglycerol triolein and glycerol [I4C] triolein or with the [I4C] triglyceride alone. A number of experiments employed [’H] oleic dispersed on albumin. All isotopic compounds were obtained from New England Nuclear and evaluated for purity by thin layer chromatography. The apo-E used in these studies was radiolabeled with”“I by the iodine monochloride tech-