AJP - Endocrinology and Metabolism, Vol 241, Issue 5 372-E377, Copyright © 1981 by American Physiological Society
Effect of exogenous estrogens on catabolism of VLDL in cholesterol-fed rabbits
R. S. Kushwaha and W. R. Hazzard
To determine the metabolic mechanism of the hypolipidemic response to
estrogen in cholesterol-fed rabbits, very low-density lipoprotein (VLDL)
apolipoprotein B (apoB) turnover studies were conducted in cholesterol-fed
animals with or without estrogen treatment. Autologous VLDL apoB had a more
rapid fractional catabolic rate (FCR) in estrogen-treated than in untreated
animals, but there was no difference in the radioactivity appearing in the
intermediate-(IDL) and low- (LDL) density lipoproteins. Similar differences
in the FCR were observed when isologous VLDL from donors in the opposite
group was injected, suggesting that estrogen treatment in cholesterol-fed
rabbits accelerated the catabolism of cholesterol- and apoE-rich
lipoproteins by a mechanism that is not dependent on its conversion to LDL.
Furthermore, VLDL apoB from normal untreated donor animals was catabolized
more rapidly in the estrogen-treated animals, but most of the radioactivity
appeared in LDL in both groups. These observations suggest that estrogen
treatment of cholesterol-fed rabbits affected only the efficiency but not
the completeness of catabolism of normal VLDL. Thus the catabolism of vLDL
in cholesterol-fed animals treated with or without estrogen depended on the
composition of VLDL injected and the pool size of plasma VLDL, which was
reduced by estrogen treatment.
