Ovarian and adrenal contributions to postnatal growth and differentiation of the rat uterus.

We tested the hypothesis that ovarian and/or adrenal factors contribute to uterine growth, differentiation, and acquisition of estrogen responsiveness in the postnatal rat. In untreated rats, normalized uterine weight (5.2 mg/10 g BW on postnatal days [PND] 1-10) increased by about 35% on PND 11-19; PND 6 ovariectomy (OVX) eliminated this increase. Adrenalectomy (ADX) on PND 6 lowered normalized uterine weight only when combined with OVX and only on PND 16 and 19, demonstrating the presence of uterotropic adrenal products. OVX +/- ADX on PND 6 delayed uterine gland genesis by about 2 days but did not alter final gland numbers. There was no change in the normal pattern of luminal epithelium morphology. A uterotropic response to 17 beta-estradiol (E2) occurred on PND 10 in OVX rats and on PND 12 in OVX + ADX rats, but not until PND 14 in controls. We conclude that normal uterine growth is independent of the ovaries and adrenals prior to PND 10, partially dependent during PND 10-15, and completely dependent during PND 16-26. Additionally, a uterotropic response to exogenous E2 occurs concomitantly with, but independently of, the endogenous estrogen surge. Finally, while uterine gland genesis is slightly retarded by OVS +/- ADX, estrogens from these organs do not induce uterine differentiation.