Journal of Lipid Research, Vol 30, 989-996, Copyright © 1989 by Lipid Research, Inc.
Metabolism of triglyceride-rich nascent rat hepatic high density lipoproteins
KE Winkler and JB Marsh
Department of Physiology and Biochemistry, Medical College of Pennsylvania, Philadelphia 19129.
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)
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