Effect of ovariectomy and replacement therapy on the tissue lipid pattern in rats

Abstract

Ovariectomy increases the percentage of total lipids in liver, kidney and uterus of intact cyclic rats. Estrogen and progesterone, when administered individually to ovariectomized rats, caused a decrease in the total lipid content of all tissues. Th effect of progesterone in estrogen-primed rats is not significant. Triglyceride and cholesterol content increases after ovariectomy; treatment with estrogen in ovariectomized rats led to a decrease in the concentration of these lipids. Progesterone has no significant effect on these lipids but showed an antagonistic action when given in estrogen-primed ovariectomized rats. The proportions of ethanolamine, choline and inositol phospholipids decreased after spaying and increased when estrogen was given to spayed rats. Progesterone alone had effect only on the uterus whereas progesterone administered to estrogen-primed rats showed an antagonistic effect in all tissues.

PIP: The changes in lipid levels of different tissues after ovariectomy and by subsequent replacement therapy were studied and the effects of estrogens and of progesterone were recorded in Wistar strain rats. Hormone therapy was begun 3 or 4 weeks after bilateral ovariectomy. Ovariectomized animals were injected in with .4 ml of hormone solution containing .2 mg of estradiol dipropionate or progesterone daily for 6 days. Control spayed rats were treated with the vehicle only. At sacrifice the liver, kidney, and uterus were removed and the lipids were extracted and purified. The purified lipids were fractionated on a silicic acid column. The various fractions were evaporated to dryness and collected in preweighted glass planchets. Neutral lipids and phospholipid were fractionated by thin layer chromatography. Details of procedures are given. The percentage of total lipids increased significantly in all tissues studied. In the neutral lipid fractions, the result was significant in the triglyceride fraction and the free cholesterol fraction. Estradiol sterols showed no significant effect. There was a significant lowering of phospholipids in the uterus and kidney tissues. Estrogen treatment decreased the lipid contents significantly in all tissues studied (p less than .01 for liver and p less than .001 for kidney and uterus), and values tended to approach the normal of the estrous stage. Progesterone also decreased the lipid content of all the tissues, but when given in estrogen-primed animals the decrease was significant only in the uterus. The phospholipid increased significantly in all tissues after estrogen treatment. Progesterone also significantly increased the phospholipid content in uterus and kidney, but less so in liver tissue. In estrogen-primed spayed rats, the progesterone treatment showed the antagonistic action of the progesterone. Progesterone also antagonized the action of estrogen on triglyceride content of different tissues.