Preparation of131I-labeled fat emulsions and distribution of the label in serum lipoproteins and lipid classes following intravenous infusion to normal and hyperlipemic subjects

Abstract

Chromatographically and radiochemically homogeneous triolein-¹³¹I was prepared from chromatographically pure triolein. Molecularly distilled and chromatographically pure cottonseed oil triglycerides were apparently labeled, in part, with several ICl molecules. These labeled triglycerides were more polar than labeled triolein and were recovered in the diglyceride fraction. Triolein-¹³¹I was therefore mixed with molecularly distilled glycerides of cottonseed oil and an emulsion was prepared that was shown to be stable after sterilization and during storage. When the labeled fat emulsion was infused in normal and hyperlipemic subjects, the label remained in the triglyceride fraction. Less than 0.1% of the label administered appeared in serum phospholipids 11 and 24 hr after the beginning of the infusion. Labeled triglycerides were first recovered in the plasma chylomicron fraction and represented exogenous lipid. The label subsequently appeared in the S_{f 10–400} lipoprotein fraction. The concentration of this endogenous lipid fraction increased and the peak in both lipid concentration and labeled lipid occurred at the same time in this lipoprotein fraction. The reappearance of labeled triglyceride in S_{f 10–400} lipoproteins provides additional information about the two-component model for the clearance of intravenous fat emulsions.