Neonatal Estrogen Treatment Research Articles

OP-12 - Three-dimensional and immunohistochemical analysis of sex steroid receptors in the developing murine mesonephros

Sex steroids are essential for the development of the reproductive tracts, and their function is mediated by activating their receptors. The expression patterns of the receptors have been investigated in previous studies, but the results differ. One of the reasons is a lack of a method to distinguish each region of the reproductive tracts. To distinguish the cranial and caudal Wolffian duct (WD), which contribute to the common efferent duct and epididymal duct, respectively, it is necessary to check the connection with the mesonephric tubules (MTs) that differentiate into the efferent ductules. In this study, we examined the expression patterns of sex steroid receptors in detail to combine the three-dimensional analysis. Serial paraffin sections of the developing murine mesonephros were prepared, and immunohistochemistry for sex steroid receptors, such as estrogen receptor (ESR1), androgen receptor (AR), and progesterone receptor (PR), was performed. Additionally, the sections in which Collagen Type IV was detected were used to reconstruct the MTs and WD. ESR1 was found in the mesenchymal cells around the WD, and the MTs and cranial WD also became positive from the middle period of the development, but the caudal WD was negative for ESR1. AR was first found at the distal end (gonadal side) of the MTs and weakly in the mesenchymal cells. The epithelial expression became strong in the whole length of the MTs and cranial portion of the WD in the middle period of the development. Finally, the caudal part of the WD also showed strong positive just before birth. PR was weakly positive in the MTs and cranial WD, but the distal end of the MTs where the rete cells were adherent was negative for PR. Androgen secreted from the gonad probably acts on the distal end of the MTs to maintain and develop the efferent tubules. ESR1 and PR may also contribute to the development of the efferent duct. Additionally, estrogen treatment in the neonatal male mice induces epididymal inflammation after puberty, but its mechanisms are still unclear. This study found the ESR1 expression in not epithelial cells but mesenchymal cells around the caudal WD. These results suggest that neonatal estrogen treatment probably affects the mesenchymal cells around the epididymal duct, resulting in the inability to suppress the autoimmune response to spermatozoa after puberty.

Neonatal estrogen treatment with β-estradiol 17-cypionate induces in post-pubertal mice inflammation in the ductuli efferentes, epididymis, and vas deferens, but not in the testis, provoking obstructive azoospermia

Neonatal estrogen treatment (NET) induces morphological changes in male reproductive organs. NET with β-estradiol 17-cypionate is reported to induce inflammation with stromal-epithelial abnormalities in the prostate and seminal vesicles in post-pubertal mice. The aim of this study was to investigate the histopathology of the testis, ductuli efferentes, epididymis, and vas deferens in mice after NET with β-estradiol 17-cypionate. No morphological changes in these organs were observed until 4weeks after NET. However, some inflammatory cells were found in epididymis and vas deferens 6weeks after NET. Eight weeks after NET, inflammatory cells spread to the ductuli efferentes and inflammation was severe from 6 to 12weeks after NET. Inflammatory cells were never seen in the whole testis, but cystic dilatation of the rete testes with spermatogenic disturbance was found around the mediastinum testis. Many inflammatory cells emigrated into the lumen of the epididymis, resulting in complete absence of spermatozoa in the vas deferens. Most of the inflammatory cells penetrating into the epithelial layers of epididymal ducts were neutrophils. These results indicate that in post-pubertal mice, NET with β-estradiol 17-cypionate induces inflammation in the ductuli efferentes, epididymis, and vas deferens, but not in the testis, provoking obstructive azoospermia.

Neonatal estrogen exposure inhibits steroidogenesis in the developing rat ovary.

Treatment of newborn female rats with estrogens significantly inhibits the growth and differentiation of the ovary. To understand the molecular mechanism of estrogen action in the induction of abnormal ovary, we examined the expression profiles of steroidogenic factor 1 (SF-1) and several of its target genes in the developing ovaries after neonatal exposure to synthetic estrogen, estradiol benzoate (EB) by using reverse transcriptase polymerase chain reaction, in situ hybridization, and immunohistochemistry. Morphologic examination indicated inhibitory effects of estrogen on the stratification of follicles and development of theca and interstitial gland during postnatal ovarian differentiation. The expression of the steroidogenic acute regulatory protein (StAR) and cholesterol side-chain cleavage cytochrome P450 (P450(SCC)), which are both essential for steroid biosynthesis, markedly decreased in theca and interstitial cells throughout the postnatal development of the EB-treated ovary. However, expression of the transcriptional activator of the two genes, SF-1 was unaffected in theca and interstitial cells, although the number of these cells was lower in the EB-treated ovary than in the control ovary. The expression of the estrogen mediator, estrogen receptor-alpha (ER-alpha), diminished specifically in theca cells at P6 and recovered by P14 in the EB-treated ovary. These results indicate that the effect of estrogens is mediated by means of ER-alpha resulting in the down-regulation of StAR and P450(SCC) genes during early postnatal development of the ovary. These results suggest that the abnormal ovarian development by neonatal estrogen treatment is closely correlated with the reduced steroidogenic activity, and the data obtained by using this animal model may account in part the mechanism for aberrant development and function of the ovary in prenatally estrogen-exposed humans.

NEONATAL ESTROGEN TREATMENT AND ITS CONSEQUENCES FOR THYMUS DEVELOPMENT, SERUM LEVEL OF AUTOANTIBODIES TO CARDIOLIPIN, AND THE DELAYED-TYPE HYPERSENSITIVITY RESPONSE

Eight-week-old female and male NMRI mice treated neonatally with the synthetic estrogen diethylstilbestrol (DES), estradiol-17 b , or tamoxifen displayed an enlarged thymus when compared with controls (approximately 1.5-fold). In control females, either ovariectomy or adrenalectomy increased thymus weight to the level characteristic for DEStreated females, but these endocrine ablations had no significant effect in DES females. The serum estrogen levels were similar in intact DES, ovariectomized DES, and ovariectomized female controls; serum corticosterone was similar in controls and DES females. The expression of the Thy1.2+ marker and the percentages of CD4+CD8+ DP and CD4+ and CD8+ SP cell subsets were similar in thymocyte populations from 8-wk-old controls and DES females; the CD4+ and CD8+ SP subsets were similar in splenocyte populations. The levels of serum immunoglobulin (Ig) G and IgM autoantibodies to cardiolipin showed age-dependent fluctuations but were similar in controls and DES females; however, the IgG autoantibodies in DES females were qualitatively different from those in controls with respect to sensitivity to bovine serum (a source of Beta2-glycoprotein I). Contrary to females, DES-treated males had higher levels of autoantibodies than controls. The delayed-type hypersensitivity (DTH) response to oxazolone was similar in controls and DES animals at 8 wk, increased in DES females and males at 6 mo, but was reduced in DES females at 1 yr. Thus, even though adult mice with thymus enlargement after neonatal estrogen treatment do not differ from controls with respect to the expression of the Thy1.2 marker or percentages of CD4+/CD8+ DP or SP subsets in thymus and spleen, qualitative and quantitative differences occur in immune parameters (autoantibodies to cardiolipin) and a T-cell-dependent immune response (DTH).

Morphological changes in mouse accessory sex glands following neonatal estrogen treatment

A single injection of beta-estradiol 17-cypionate into the mice within 5 hr after birth induced inflammation in all prostate lobes and the seminal vesicles. Neutrophils emigrated into the lumen through the basal lamina and epithelium of the seminal vesicle and the anterior prostate. Local infiltration of lymphocytes was observed in the stroma and epithelium of ventral prostates. Lymphocytes penetrated through smooth muscle cells into epithelium. This could support the hypothesis that smooth muscle cells are the target of the estrogen action of prostates in estrogenized animals.

Neural tissue‐specific epidermal growth factor (EGF)‐like domain containing protein, NEII2, plays an important role in the central regulation of puberty onset in the female rat hypothalamus

In the present study we determined if NELL2, a neural tissue‐specific protein containing 6 epidermal growth factor (EGF)‐like repeat domains, plays an important role in the regulation of puberty initiation in the rat hypothalamus. We originally found that NELL2 is a new estrogen‐responsive gene in hypothalami derived from estrogen‐sterilized and control rats using a PCR differential display. In the 40‐day‐old female rat hypothalamus, NELL2 was up‐regulated by neonatal estrogen treatment. In situ hybridization his to chemistry showed that NELL2 is very abundant in the ventromedial hypothalamic nucleus that is responsible for the control of sex behavior. NELL2 mRNA level in the medial basal hypothalamus showed a dramatic increase before female puberty onset, which suggests that NELL2 may be involved in the process regulating female puberty onset. We attemped to block NELL2 synthesis with intrace rebroventricular injection of an antisense oligodeoxynucleotide (ODN) to the NELL2 mRNA, and examined its effect ...

Permanent effects of neonatal estrogen exposure in rats on reproductive hormone levels, Sertoli cell number, and the efficiency of spermatogenesis in adulthood.

This study aimed to identify the mechanism(s) for impairment of spermatogenesis in adulthood in rats treated neonatally with estrogens. Rats were treated (days 2-12) with 10, 1, or 0.1 microg diethylstilbestrol (DES), 10 microg ethinyl estradiol (EE), 10 mg/kg of a GnRH antagonist (GnRHa), or vehicle and killed in adulthood. DES/EE caused dose-dependent reductions in testis weight, total germ cell volume per testis, and Sertoli cell volume per testis. Sertoli cell number at 18 days of age in DES-treated rats was reduced dose dependently. GnRHa treatment caused changes in these parameters similar to those in rats treated with 10 microg DES. Plasma FSH levels were elevated (P < 0.001) to similar levels in all treatment groups regardless of differences in Sertoli cell number and levels of inhibin B; the latter reflected Sertoli cell number, but levels were disproportionately reduced in animals treated with high doses of DES/EE. Neonatal estrogen treatment, but not GnRHa, caused dose-dependent reductions (40-80%) in plasma testosterone levels in adulthood, but did not alter LH levels. Preliminary evidence suggests that the decrease in testosterone levels in estrogen-treated rats is not due to reduced Leydig cell volume per testis. GnRHa-treated rats exhibited a significant increase in germ cell volume per Sertoli cell and a reduction in germ cell apoptosis, probably because of the raised FSH levels. Despite similar raised FSH levels, rats treated with DES (10 or 1 microg) or EE (10 microg) had reduced germ cell volume/Sertoli cell and increased germ cell apoptosis, especially when compared with GnRHa-treated animals. The latter changes were associated with an increase in lumen size per testis, indicative of impaired fluid resorption from the efferent ducts, resulting in fluid accumulation in the testis. Rats treated neonatally with 0.1 microg DES showed reduced germ cell apoptosis comparable to that in GnRHa-treated animals. The changes in apoptotic rate among treatment groups occurred across all stages of the spermatogenic cycle. It is concluded that 1) neonatal estrogen treatment results in dose-dependent alterations in Sertoli cell numbers, germ cell volume, efficiency of spermatogenesis, and germ cell apoptosis in adulthood; 2) the relatively poor spermatogenesis in estrogen-treated animals is most likely due to altered testis fluid dynamics and/or altered Sertoli cell function; 3) as indicated by FSH (LH) and testosterone levels, the hypothalamic-pituitary axis and Leydig cells are probably more sensitive than the Sertoli cells to reprogramming by estrogens neonatally; and 4) elevated FSH levels in adulthood may improve the efficiency of spermatogenesis.

Immunohistochemical studies on the expression and estrogen dependency of EGF and its receptor and C‐fos proto‐oncogene in the uterus and vagina of normal and neonatally estrogen‐treated mice

Background The final target cell response to estrogen is dependent not only on the estrogen receptor, but also on autocrine/paracrine interactions with growth factors (e.g., EGF) and proto-oncogenes (e.g., c-fos). Because neonatal estrogen treatment results in permanent changes in the female mouse genital tract (permanent vaginal cornification, cervical adenosis and tumors, changed growth control mechanisms in uterus), it was of interest to study possible acute and permanent effects of such treatment on distribution and levels of EGF, its receptor (EGF-r), and c-fos and to relate such changes to morphological development and appearance of epithelial abnormalities. Methods Immunohistochemical techniques using frozen sections from the uterus and vagina of neonatal and adult (ovariectomized, estradiol-treated) females, treated with olive oil or diethylstilbestrol in neonatal life. Results A difference in stromal-epithelial distribution of EGF was demonstrated with respect to region studied (uterus, vagina) and age (neonatal, adult). EGF was localized mainly in the uterine stroma but in both vaginal epithelium and stroma (with a different pattern compared to uterus). In neonatal females, EGF occurred in both tissue components in both regions, and the distribution pattern was quite different from that in adult females. The EGF level was increased by estrogen in adult but not in neonatal females. EGF-r and c-fos occurred in both uterine epithelium and stroma and in the vaginal epithelium; levels and distribution pattern were affected by estrogen. Neonatal estrogen treatment increased the levels of uterine EGF and c-fos in adult life. Conclusions There are distinct developmental changes in the distribution and estrogen sensitivity of EGF. Only further studies can prove or disprove the association between the earlier reported disturbed growth control mechanisms in the uterus of adult but neonatally estrogen-treated females and the increased levels of uterine EGF and c-fos. The present results do not seem to explain mechanisms involved in the origin of neonatally estrogen-induced cervicovaginal epithelial abnormalities, nor do they explain the earlier described difference in estrogen-induced proliferative response between the uterine cervix and uterus proper. © 1996 Wiley-Liss, Inc.

Immunohistochemical studies on the expression and estrogen dependency of EGF and its receptor and C-fos proto-oncogene in the uterus and vagina of normal and neonatally estrogen-treated mice.

The final target cell response to estrogen is dependent not only on the estrogen receptor, but also on autocrine/paracrine interactions with growth factors (e.g., EGF) and proto-oncogenes (e.g., c-fos). Because neonatal estrogen treatment results in permanent changes in the female mouse genital tract (permanent vaginal cornification, cervical adenosis and tumors, changed growth control mechanisms in uterus), it was of interest to study possible acute and permanent effects of such treatment on distribution and levels of EGF, its receptor (EGF-r), and c-fos and to relate such changes to morphological development and appearance of epithelial abnormalities. Immunohistochemical techniques using frozen sections from the uterus and vagina of neonatal and adult (ovariectomized, estradiol-treated) females, treated with olive oil or diethylstilbestrol in neonatal life. A difference in stromal-epithelial distribution of EGF was demonstrated with respect to region studied (uterus, vagina) and age (neonatal, adult). EGF was localized mainly in the uterine stroma but in both vaginal epithelium and stroma (with a different pattern compared to uterus). In neonatal females, EGF occurred in both tissue components in both regions, and the distribution pattern was quite different from that in adult females. The EGF level was increased by estrogen in adult but not in neonatal females. EGF-r and c-fos occurred in both uterine epithelium and stroma and in the vaginal epithelium; levels and distribution pattern were affected by estrogen. Neonatal estrogen treatment increased the levels of uterine EGF and c-fos in adult life. There are distinct developmental changes in the distribution and estrogen sensitivity of EGF. Only further studies can prove or disprove the association between the earlier reported disturbed growth control mechanisms in the uterus of adult but neonatally estrogen-treated females and the increased levels of uterine EGF and c-fos. The present results do not seem to explain mechanisms involved in the origin of neonatally estrogen-induced cervicovaginal epithelial abnormalities, nor do they explain the earlier described difference in estrogen-induced proliferative response between the uterine cervix and uterus proper.

Acute and permanent growth effects in the mouse uterus after neonatal treatment with estrogens

Acute and late effects of neonatal estrogen treatment were studied in NMRI mice treated with diethylstilbestrol (DES) or estradiol-17β (E 2) on days 1 to 5 after birth (estrogenized females). The uterine wet weight (UWW) response in 6-day-old females, after 5 daily treatments with DES, had a peak at a daily dose of 10 −2 μg DES and declined with higher doses. Females (26-day-old) treated with DES or E 2 neonatally had a reduced UWW response to a challenge with DES; on a dose basis, DES was more effective neonatally than E 2. A single injection with DES or E 2 in the neonatal period stimulated mitotic activity in the uterine horn epithelium; the UWW response to a 24-h DES pulse increased from day 2 to 6 after birth, but the uterine epithelial mitotic rate response decreased. Epidermal growth factor (EGF) was a more potent stimulator of mitotic activity than DES or E 2. DES inhibited mitotic activity in the uterine cervical epithelium; EGF protected from this DES effect. In adult estrogenized females; EGF-induced uterine stimulation of 3H-thymidine incorporation subsided more rapidly than in control females; uterine epithelium did not respond to EGF in vitro. Uterine stroma of adult estrogenized females is postulated to house a population of cells under nonovarian proliferation control while the uterine epithelium may be under influence of an ovary-dependent proliferation inhibiting factor that is gradually lost under culture conditions.

Effects of testosterone and estrogen on hepatic levels of cytochromes P450 2C7 and P450 2C11 in the rat

The effects of exogenous hormone treatment on the expression of cytochromes P450 2C7 and P450 2C11 were studied in neonatally gonadectomized and shamoperated male and female rats. Hepatic levels of cytochrome P450 2C7 were found to be two- to threefold higher in intact adult female versus male rats. Neonatal gonadectomy resulted in a reversal of the relative cytochrome P450 2C7 levels in male and female animals at maturity. Expression of this isozyme was restored in ovariectomized females by estradiol treatment. Furthermore, neonatal and/or pubertal administration of estradiol to intact male rats induced cytochrome P450 2C7 to adult female levels. On the other hand, administration of testosterone at all times examined had no effect in intact female rats, but decreased cytochrome P450 2C7 to normal levels in neonatally castrated males treated during adulthood. Neonatal testosterone treatment also increased hepatic cytochrome P450 2C7 content in both ovariectomized females and intact males. These results indicate that estrogen is required for full expression of cytochrome P450 2C7 while the effect of testosterone is ambiguous. In comparison, neonatal gonadectomy of male rats abolished the adult expression of cytochrome P450 2C11. Normal levels were restored only by treatment with testosterone during adulthood. Neonatal testosterone treatment did not induce cytochrome P450 2C11 levels in gonadectomized rats of either sex. In contrast, neonatal estrogen treatment suppressed cytochrome P450 2C11 expression in intact adult male rats to the same extent as neonatal castration. These results indicate that androgen exposure during the adult, and not the neonatal, phase is essential for full expression of cytochrome P450 2C11.

ALTERATION OF PROTO-ONCOGENE C-FOS EXPRESSION IN NEONATAL ESTROGENIZED BALB/C FEMALE MICE &amp; MURINE CERVICOVAGINAL TUMOR LJ6195

Experiments were performed to determine the effect of neonatal estrogen treatment on the expression of the proto-oncogene c-fos in the BALB/c mouse cervicovaginal tract. Estradiol induces the expression of c-fos in the normal mouse cervicovaginal tract. However, c-fos expression was not stimulated by estradiol in the cervicovaginal tracts of mice that received neonatal estrogen treatment. In addition, the level of expression of c-fos by the estrogen- and progesterone-induced murine cervicovaginal LJ6195 tumor was similar to that in the normal vaginal tract following estradiol stimulation and was not regulated by estradiol.

Body weight rhythmicity in the unweaned female rat following neonatal estrogen treatment

Male and female rats were weighed daily throughout this study to determine whether neonatal exposure to estrogens influences body weight (BW) patterns, particularly during the period before weaning when vaginal opening (VO) occurs as a consequence of this treatment. Females receiving estradiol benzoate (EB) at the age of 5 days had greater body weight than their controls soon after the treatment and until day 21. Clear 3-day periodic changes of BW, between days 9 and 20, were revealed by the spectral analysis of the results in EB-given females which did not occur in their controls. Changes of BW (at 4-day intervals) were verified in adult control females whereas age-matched EB-treated females did not show such a rhythm. Neither BW gain nor infradian rhythmicity were detected in infantile males after neonatal EB treatment. The results suggest that, as in spontaneous puberty, a relationship between the occurrence of VO and the establishment of the infradian body rhythmicity in the infantile estrogenized female may exist.

Induction of estrogen receptor, peroxidase activity, and epithelial abnormalities in the mouse uterovaginal epithelium after neonatal treatment with diethylstilbestrol.

Neonatal female NMRI mice were treated with daily doses of 10(-2) or 5 micrograms diethylstilbestrol (DES) on one or more of days 1-5 after birth. Using immunohistochemical techniques and a monoclonal antibody to the estrogen receptor, we demonstrated an estrogen-induced precocious appearance of receptor protein in the nuclei of the uterovaginal epithelium. High levels of peroxidase activity and a pronounced stromal infiltration with peroxidase positive cells occurred in the uterine cervix and upper vagina after estrogen treatment. This regional restriction in peroxidase activity was similar to the regional restriction for estrogen-induced epithelial abnormalities (heterotopic columnar epithelium, adenosis). A combined treatment with DES and corticosterone depressed peroxidase activity but not to the control level. The distribution of abnormal epithelium was similar in DES- and DES-corticosterone-treated females. The conclusion is that neonatal estrogen treatment induces an epithelial receptor for estrogen and a high level of cervical peroxidase activity, but the relationship between these parameters and the appearance of abnormal cervicovaginal epithelial changes could not be settled in the present study.

Sexual differentiation of androgen-sensitive and estrogen-sensitive regulatory systems for aggressive behavior

CF-1 female mice were treated with either testosterone (T), diethylstilbestrol (DES), or methyltrienolone (R1881) on the day of birth and were subsequently tested for their responsiveness to the aggression-promoting property of androgen or estrogen during adulthood. The results showed that neonatal exposure to androgen enhanced subsequent sensitivity to androgenic stimulation but did not alter responsiveness to estrogens. Neonatal estrogen treatment established the capacity to exhibit aggression in response to estrogenic stimulation in adulthood but had little effect on responsiveness to androgens. These data indicate that the androgenic and estrogenic metabolites of T have distinct roles in masculinization of the neural substrate for aggressive behavior.

Inhibition of testicular development and feminization of the male genitalia by neonatal estrogen treatment in a marsupial.

Differentiation of the mammalian gonad is thought to be constitutive, occurring independently of and not significantly altered by gonadal hormones. In this study, estradiol benzoate (EB) and testosterone propionate (TP) were administered to newborn gray opossums (Monodelphis domestica) during the first week after birth. It was found that males and females treated with TP and females treated with EB developed normally. In males treated with EB on both Day 1 and Day 3 of postnatal life, gonads did not differentiate and internal and external genitalia were feminine. These findings are discussed with respect to current theories of mammalian sexual differentiation.

Effects of neonatal estrogen treatment of female guinea pigs on mounting behavior in adulthood

Female guinea pigs were treated with 200 μg estradiol dipropionate (ED) daily from Days 1 to 15 of life. As adults they all ovulated. After gonadectomy and estrogen-progesterone treatment in adulthood, lordosis behavior was evident and showed no decrements (compared with neonatally oil-treated controls) except for a marginal decrease in maximum duration scores. However, testosterone propionate treatment in adulthood significantly increased mounting behavior in neonatally ED-treated females compared to the controls. On the other hand, estrogen-progesterone treatment in adulthood stimulated mounting in the neonatally oil-treated group, but not in the neonatally estrogenized group. The results suggest that at least some aspects of steroid-dependent behaviors can be permanently influenced by estrogen treatment after the presumed prenatal critical period for sexual differentiation has been completed in guinea pigs.

Origin of permanently altered epithelial cells of the vagina in neonatally estrogen-treated mice.

In adult mice, neonatal injections of estrogen induce persistent, estrogen-independent cornification of the vaginal epithelium. Since the occurrence of nodules composed of affected epithelial cells (B cells) is a prodromic phenomenon of the irreversible vaginal alterations, the relationship between the occurrence of B-cell nodules and the time of DNA synthesis in the vaginal epithelial cells was examined by means of the techniques of serial mapping and autoradiography. B-cell nodules appeared in the epithelium of mullerian vagina 3-5 days after the initiation of neonatal estrogen treatment, without spatial continuity to cuboidal epithelial cells of the sinus vagina. The time of DNA synthesis was different in B cells from that in both columnar mullerian and cuboidal sinus cells, suggesting that the mother cells of B cells might be a population of still unidentified, undifferentiated cells.

Dynamics of the estrogen receptor in the uteri of mice treated neonatally with estrogen.

Experiments were performed to examine the uterine response to estrogen and the dynamics of uterine estrogen neonatally. Uterine tissue of neonatally estrogenized mice showed a markedly reduced response to estrogen in the adult. The concentration of cytoplasmic estrogen receptor in the uteri of such mice was markedly lower than that of neonatally vehicle-injected control mice. Nuclear and cytoplasmic estrogen receptors of uteri in both groups were determined by the exchange assay at various intervals after injection of estradiol. Nuclear translocation of estrogen receptor complexes in neonatally estrogenized mice was similar to that in control mice. The concentration of cytoplasmic receptor decreased to low levels by 1 h and began a gradual increase from 1-16 h after injection in both groups. Between 16-24 h after injection, however, the level of cytoplasmic receptor continued to increase in control mice but almost ceased to increase in neonatally estrogenized mice. Ten daily injections of estradiol continued to increase the concentration of cytoplasmic estrogen receptor in control mice. On the other hand, in neonatally estrogenized mice treated daily with estradiol, the receptor level reached a plateau on day 5. These data suggest that the induction of new uterine estrogen receptor under the influence of estrogen may be altered by neonatal estrogen treatment.

Neonatal estrogen treatment alters sexual differentiation of hepatic histidase.

Hepatic histidase was used as an enzyme marker for the study of neonatal programming in intact rats. Diethylstilbestrol (DES) or 17 beta-estradiol (E2) treatment for days, 2, 4, and 6 post partum resulted in decreased histidase activities in the adult female, but no effect was seen in prepubertal male and female rats or in adult males. In contrast, similar neonatal doses of testosterone propionate (TP) had no effect on histidase. Dose-response experiments demonstrate a 3-fold greater neonatal sensitivity to DES than to E2. The action of neonatal estrogen treatment is demonstrated to be permanent and irreversible. Neonatal treatment with E2, DES, or TP resulted in decreased uterine wet weights in adult females (E2 less than DES less than TP less than controls). Circulating sera estrogen levels were lower in adult E2- and DES-treated females than in TP-treated and control females. Our results suggest that these alterations may be due to direct toxic effects on the postnatal development of the female reproductive tract and endocrine system and/or to organizational effects on nerve endings in the hypothalamus that result in programming for altered sexual differentiation of hepatic metabolism.