Metabolism of triglyceride-rich nascent rat hepatic high density lipoproteins.
Nascent high density lipoprotein (HDL) and nascent very low density lipoprotein (VLDL) were isolated from rat livers that had been perfused with [3H]glycerol to label the triglyceride. When injected into intact rats, the labeled HDL-triglyceride disappeared as rapidly as the VLDL-triglyceride, with only 10% of the injected label remaining in the plasma after 30 min. The protein moiety of nascent HDL was labeled with [35S]methionine in a similar fashion and the labeled nascent HDL was separated into nonretained (NR) and retained (R) fractions by heparin-Sepharose affinity chromatography. When injected into rats, 55% of the injected label in nascent fraction NR and 72% of that in nascent fraction R was recovered from plasma at 30 min, compared to only 10% of the triglyceride label from unfractionated nascent HDL, indicating dissociation of triglyceride and apolipoprotein clearance. The plasma decay curves for both triglyceride and protein were biexponential. By 5 min, 15% of the 35S label remaining in plasma represented apoE and apoC that had been transferred from nascent HDL fractions NR and R to the d less than 1.063 g/ml fraction of plasma. Plasma HDL was labeled in vivo with [35S]methionine, separated into fractions NR and R, and the clearance of the two plasma HDL fractions was compared with that of the corresponding nascent HDL fractions. Except for a faster rate of removal of the nascent HDL fractions during the first 5 min, the serum decay curves were very similar.(ABSTRACT TRUNCATED AT 250 WORDS)
Winkler
K E
KE
Department of Physiology and Biochemistry, Medical College of Pennsylvania, Philadelphia 19129.
Marsh
J B
JB
D000818:Animals; D001053:Apolipoproteins / Q000378:metabolism; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008079:Lipoproteins, VLDL / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D008657:Metabolic Clearance Rate; D008715:Methionine; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D013462:Sulfur Radioisotopes; D014280:Triglycerides / Q000378:metabolism*
D001053:Apolipoproteins; D008075:Lipoproteins, HDL; D008079:Lipoproteins, VLDL; D013462:Sulfur Radioisotopes; D014280:Triglycerides; D008715:Methionine