Failure of testosterone propionate to induce the 'early-androgen' syndrome in rats previously injected with progesterone

Effect of intrauterine position of conceptus development, placental and endometrial release of progesterone and estrone in vitro, and concentration of steroid hormones in fetal fluids throughout gestation in swine

Twenty intact and 25 unilaterally hysterectomized-ovariectomized gilts were used to study the effect of fetal intrauterine position on conceptus development, concentrations of endogenous progesterone (P4) and estrone (E1) in the placenta and endometrium, and steroid hormone concentrations in amniotic and allantoic fluids during gestation. Gilts were hysterectomized at 40, 60, 80, or 100 d of gestation. Placental and endometrial tissues were pooled individually by the intrauterine position of the associated fetus and incubated separately, and concentrations of P4 and E1 in the medium were determined. Uterine status (intact or unilaterally hysterectomized-ovariectomized) did not affect any of the variables measured. Intrauterine position affected fetal and placental weights (P < 0.02 and 0.01, respectively) only at Day 40 of gestation. The weights of female fetuses bordered in utero by two males and their associated placentas were lower than those from other intrauterine positions. Intrauterine position had no effect on placental and endometrial P4 release or on E1, P4, and androgen concentrations in fetal fluids at any stage of gestation. At Day 100 of gestation, placentas associated with fetuses bordered by those of the same sex released more E1 than did placentas associated with fetuses bordered by those of the same opposite sex (P < 0.01). This study indicates that intrauterine position in swine has a limited effect on conceptus development and on placental and endometrial steroidogenic activity.

Effects of neonatal exposure to the antiprogestin mifepristone, RU 486, on the sexual development of the rat

RU 38486 (RU 486, mifepristone) is a potent progesterone receptor antagonist that has been used in humans in the pharmacologic induction of abortion. The effects of exposure to RU 486 during the neonatal period of the rat has not been previously reported. We examined the consequences of such exposure in the context of sexual development. Long-Evans rat pups were subcutaneously injected with either 100 micrograms RU 486, 300 micrograms RU 486, 500 micrograms progesterone (P), or 50 micrograms testosterone propionate (TP) in 0.05 ml sesame oil, or oil vehicle alone within 8 hours of birth, and 24 and 48 hours later. Treatment with either dose of RU 486 significantly advanced the onset of vaginal opening in females and attenuated defeminization of the lordosis response measured in males castrated as adults. As expected, TP-treated subjects were masculinized and defeminized, with females displaying fused vaginas and neither males nor females demonstrating lordosis behavior. Treatment with P caused no significant alterations in either the timing of vaginal opening or sexual behavior. These results indicate that RU 486 has clear developmental effects in the rat. Since this may well be a result of progesterone receptor blockade, further research is needed to clarify the processes involved.

Progestin receptor cells in mouse cerebral cortex during early postnatal development: a comparison with preoptic area and central hypothalamus using autoradiography with [125I]progestin

The distribution of progestin target cells in the cerebral cortex and the effect of estrogen treatment was assessed during the critical period of brain development and compared with the preoptic/central hypothalamic regions. [125I]progestin was injected into 0, 2, 8, and 12 day postnatal mice pretreated for 3 days with oil, 5 micrograms/100 g b, wt., or 100 micrograms/100 g b. wt. of estradiol dissolved in oil. Two hours after injection of radiolabeled ligand, brains were frozen and processed for thaw-mount autoradiography. At birth, labeled cells were detected in the deep (lamina VI) and intermediate (lamina V) layers of the lateral cortical regions, increased in laminae V-VI of the lateral cortex and laminae II-VI of the cingulate/paracingulate cortex at days 2 and 8, and decreased throughout the cortex by day 12. Pretreatment of animals with estradiol had no noticeable effect on the nuclear concentration of [125I]progestin in cortical cells, while estrogen weakly enhanced labeling in preoptic/central hypothalamic regions at day 2 and markedly augmented labeling in the 8 and 12 day brain. The results demonstrated that progestin receptor cells are present in the postnatal dorsal cortex, preoptic area, and hypothalamus and that the topography of cortical progestin target cells differs in part from that of estrogen target cells reported earlier.

Prenatal ethanol and the prepubertal sexually dimorphic nucleus of the preoptic area

The volume of the sexually dimorphic nucleus of the preoptic area of the hypothalamus (SDN-POA) was determined in 14-31-day-old male and female rats whose mothers received a liquid diet containing 5% w/v ethanol from day 8 of gestation to parturition. Pair-fed dams received as a nutritional control an equal volume of an isocaloric liquid diet with maltose-dextrin in place of ethanol. Normal controls had laboratory rat chow and water available ad lib. The SDN-POA volume of ethanol-exposed males was significantly reduced compared to the pair-fed and normal males, and became indistinguishable from the SDN-POA volumes of the pair-fed and normal females. Ethanol-treated females also had a markedly reduced SDN-POA volume compared to the pair-fed and normal females. Our findings indicate that the SDN-POA of prepubertal rats of both sexes is sensitive to the effects of in utero ethanol exposure. While plasma testosterone, progesterone and estradiol titers, which we measured in fetuses on gestation day 22, were differentially affected by maternal ethanol consumption, the alterations by themselves cannot adequately explain the effects of prenatal ethanol exposure on the developing SDN-POA.

Effects of neonatal testosterone and progesterone on open-field behaviour in the rat

Rats treated on the day of birth with progesterone (50 üg) or testosterone pro-pionate (200 üg) or the oil injection vehicle alone were tested in the open-field on four consectuve days at 45 days and 85 days of age. Averages across treatments showed that females ambulated more and reared more than males at both ages, that they groomed more than males at 45 days of age, and defaecated less at 85 days of age. Progesterone treatment significantly reduced defaecation in males at 45 days of age, and reduced grooming in both sexes. At 85 days of age progesterone significantly increased activity in females. Testosterone-treated animals of both sexes groomed significantly less than same-sex controls at 45 days of age, whereas at 85 days of age activity scores were significantly reduced only in females although testosterone treated males were less active on 2 test days and more active on 1. Early postnatal treatment with progesterone appeared to feminise male rats, and testosterone to masculinise female rats. Both hormones also altered the behaviour of opposite sexed rats, indicating that male rats may be further masculinised by exogenous testosterone and female rats further feminised by progesterone. Progesterone may have acted as an anti-androgenic agent by blocking gonadal and adrenal androgens in males and adrenal androgens in females.