Response of Rat Ovarian Cholesterol to Gonadotropins and Anterior Pituitary Hormones1

Abstract

The ester and free cholesterol fractions in the immature rat ovary have been studied following administration of gonadotropins and anterior pituitary hormones. Pregnant mare''s serum (PMS) and human chorionic gonadotropin (HCG) caused a great increase in ovarian size with a marked accumulation of cholesterol. Two to 3 times more ester cholesterol was present than free cholesterol. The largest ovaries with the highest free cholesterol values were seen in ovaries treated with HCG in addition to PMS. Luteinizing hormone (NIH-LH-S9) caused a marked depletion of ester cholesterol in 3 -5 hr. which was followed by a reaccumulation 18 hr. after LH administration. A small change in free cholesterol occurred during this time. A single reproducible area of ester cholesterol depletion was noted with LH doses from 0.02 to 2.0 [mu]g. Free cholesterol concentration remained relatively constant over the dosage interval. Doses of LH above 2 [mu]g did not cause further reduction in ester cholesterol. Other pituitary hormones did not significantly affect ovarian cholesterol under the experimental conditions studied. Thus, it was ester cholesterol which showed the greater changes following luteinizing stimulation. The relation of these observations to other experiments on ovarian cholesterol and steroid metabolism is discussed.