The Effects of Estrogen Administration on Plasma Lipoprotein Metabolism in Premenopausal Females

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Abstract
The effects of estrogen administration (ethinyl estradiol; 0.1 mg, orally, daily) on plasma lipoprotein metabolism were investigated in five normolipidemic premenopausal females. Estrogen administration resulted in significant (P < 0.05) mean increases in plasma cholesterol, triglyceride, very low density lipoprotein (VLDL)-cholesterol, and high density lipoprotein (HDL)-cholesterol of 18.8%, 87.0%, 123.1%, and 38.3%, respectively. Analytical ultracentrifugation demonstrated that HDL increases occurred mainly in the HDL2b subtraction(150.0% increase). Lipoprotein compositional analysis showed that estrogen administration caused significant increases in all VLDL and HDL constituents (protein, cholesterol, phospho-lipid, and triglyceride) as well as VLDL apolipoprotein (apo) B (118.9% increase) and HDL apoA-I (27.4% increase). No significant changes in LDL constituents were noted. Measurement of lipoprotein lipase and hepatic lipase enzymic activity in post-heparin plasma revealed no major change in lipoprotein lipase activity, but showed a significant decrease (43.8%) in hepatic lipase activity during estrogen administration. Radioiodinated VLDL and HDL kinetic data indicated increased VLDL apoB (86.1% rise) and HDL apoA-I (24.9% rise) synthesis during estrogen administration. These data are consistent with the concept that estrogen administration at the dose level studied in premenopausal females causes significant elevations in VLDL and HDL constituents, associated with enhanced production of VLDL apoB and HDL apoA-I.