Effect of Estrogens on Rat Serum Lipoproteins

Abstract

Estrogens, ingredients of contraceptive drugs, were found to affect serum lipids, lipoproteins, and liver lipids of rats selectively. Subcutaneous administration of ethynylestradiol reduced the phospholipid content of the dextran sulfate soluble fraction (HDS) of the serum and decreased the rate of disappearance of the phospholipid moiety, labelled with choline-Me3H in this fraction. Estradiol-17β increased the HDS phospholipid but not its rate of turnover. On analytical ultracentrifugation of the whole serum, no low density lipoprotein was detected and the high density lipoprotein was reduced in ethynylestradiol-treated rats. Ethynylestradiol decreased the phospholipid content and turnover of lecithin in the liver. Both ethynylestradiol and estradiol-17β quantitatively increased the very low density lipoprotein, increasing the phospholipid and triglyceride contents. Data suggested that ethynylestradiol and estradiol-17β affected phospholipid synthesis in the liver to different degrees and one result of this was a change in the proportion of phospholipid in the high density lipoprotein in the rat.