Effect of exogenous estrogens on catabolism of VLDL in cholesterol-fed rabbits.
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.
D000818:Animals; D001053:Apolipoproteins / Q000378:metabolism; D001055:Apolipoproteins B; D002791:Cholesterol, Dietary / Q000494:pharmacology*; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D008074:Lipoproteins / Q000097:blood; D053419:Lipoproteins, IDL; D008077:Lipoproteins, LDL / Q000097:blood; D008079:Lipoproteins, VLDL / Q000097:blood*; D011817:Rabbits
D001053:Apolipoproteins; D001055:Apolipoproteins B; D002791:Cholesterol, Dietary; D008074:Lipoproteins; D053419:Lipoproteins, IDL; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D004958:Estradiol; C007630:estradiol 17 beta-cypionate