Journal of Lipid Research, Vol 24, 1475-1484, Copyright © 1983 by Lipid Research, Inc.
Lipoprotein metabolism in the ovariectomized rat
BJ van Lenten, GW Melchior and PS Roheim
The hyperlipoproteinemia observed after ovariectomy in rats was previously
shown to be associated with increased concentrations of cholesterol,
triglycerides, and apolipoproteins B, E, and C. In the present study, it
was shown that increases in low density lipoproteins and high density
lipoproteins were almost entirely responsible for the changes in plasma
lipids and apolipoproteins after ovariectomy. The size of the low density
lipoproteins and high density lipoproteins isolated from the plasma of
ovariectomized rats as determined by agarose chromatography appeared to be
somewhat different from that of control rats. Specifically, the
apolipoprotein B appeared to be associated with somewhat smaller particles,
whereas the apolipoprotein E from those rats appeared to be associated with
larger particles than that of control rats. To determine the mechanism for
the increased plasma low density lipoproteins, apolipoprotein B pool sizes
and turnover rates were calculated and compared. In addition to an
increased mass of low density lipoproteins in ovariectomized rats, the
turnover rate of low density lipoproteins was increased almost twofold,
indicating an increased low density lipoprotein synthesis and catabolism in
those animals. We postulate that the increased low density lipoprotein
levels of ovariectomized rats are due to an initial increased production of
low density lipoproteins, followed by an enhanced catabolism of low density
lipoproteins to establish a steady state at higher plasma low density
lipoprotein concentrations.
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