Sites of Androgen and Estradiol Production in the Second Half of Pregnancy in the Rat1

Abstract

To determine the sites of androgen and estradiol production in the second half of pregnancy, pregnant rats were hypophysectomized or hypophysectomized and hysterectomized on Day 12. After hypophysectomy, the luteal weight, the concentration of androgen and estradiol in corpora lutea, and serum androgen remained at control values on Days 14, 18, and 22. In contrast, by Day 14 the nonluteal tissue atrophied, its estradiol concentration decreased, and serum estradiol declined from 25 ± 1.0 in sham-treated animals to 21 ± 0.3 pg/ml. When the conceptuses were removed together with the pituitary by hypophysectomy and hysterectomy on Day 12, androgen and estradiol levels in the serum dropped to barely detectable levels. To determine whether the placentas secreted androgen or stimulated androgen secretion by other endocrine glands, adrenals, ovaries, and/or fetuses were removed from rats hypophysectomized on Day 12, and pregnancy was maintained with progesterone treatment. No decrease in androgen levels in the serum was observed. Serum androgen remained elevated in all groups in which the placentas remained in utero. When the placentas were removed, as in hypophysectomized-hysterectomized rats, serum androgen dropped dramatically. However, while androgen levels remained elevated, serum estradiol declined after either ovariectomy or fetectomy and a synergism was observed when ovariectomy and fetectomy were combined. These results indicate that the placentas are a source of androgen in the second half of pregnancy and that the ovaries and fetuses are a site of estradiol production.