Chylomicron remnant cholesteryl esters as the major constituent of very low density lipoproteins in plasma of cholesterol-fed rabbits.
Feeding rabbits 500 mg of cholesterol daily for 4 to 15 days greatly increased the concentration of esterified cholesterol in lipoproteins of d less than 1.006 g/ml. The origin of hypercholesterolemic very low density lipoproteins was investigated by monitoring the degradation of labeled lymph chyomicrons administered to normal and cholesterol-fed rabbits. Chylomicrons were labeled in vivo by feeding either 1) [3H]cholesterol and [14C]oleic acid or 2) [14C]cholesterol and [3H]retinyl acetate. After intravenous injection of labeled chylomicrons to recipient rabbits, [14C]triglyceride hydrolysis was equally rapid in normal and cholesterol-fed animals. Normal rabbits rapidly removed from plasma both labeled cholesteryl and retinyl esters, whereas cholesterol-fed rabbits retained nearly 50% of doubly labeled remnants in plasma 25 min after chylomicron injection. Ultracentrifugal separation of plasma into subfractions of very low density lipoproteins showed that chylomicron remnants in cholesterol-fed animals are found among all subclasses of very low density lipoproteins. Analysis of cholesteryl ester specific activity-time curves for the very low density lipoproteins subfraction from hypercholesterolemic plasma showed that nearly all esterified cholesterol in large very low density lipoproteins and approximately 30% of esterified cholesterol in small very low density lipoproteins was derived from chylomicron degradation. Apparently, nearly two-thirds of the esterified cholesterol in total very low density lipoproteins from moderately hypercholesterolemic rabbits is of dietary origin.
D000818:Animals; D002250:Carbon Radioisotopes; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000494:pharmacology; D002788:Cholesterol Esters / Q000097:blood*; D002791:Cholesterol, Dietary; D002914:Chylomicrons / Q000097:blood*; D004036:Diet, Atherogenic; D005260:Female; D007553:Isotope Labeling; D007700:Kinetics; D008079:Lipoproteins, VLDL / Q000097:blood*; D011817:Rabbits; D013997:Time Factors; D014316:Tritium
D002250:Carbon Radioisotopes; D002788:Cholesterol Esters; D002791:Cholesterol, Dietary; D002914:Chylomicrons; D008079:Lipoproteins, VLDL; D014316:Tritium; D002784:Cholesterol