The postnatal ontogeny of rat uterine glands and age-related effects of 17 beta-estradiol

Irreversible effects of neonatal exposure to p-tert-octylphenol on the reproductive tract in female rats

It has been known for many years that administration of androgens or estrogens at critical periods of development in mammals causes severe long-term effects on the endocrine/genital systems. The environmental pollutant p-tert-octylphenol (OP) possesses a weak but clear estrogen agonist activity in in vitro and in vivo studies. In the present study, effects of neonatal exposure to OP on the reproductive tract of female rats were investigated. Newborn female pups were injected with 100 mg/kg OP subcutaneously within 24 h after birth. Administration was repeated every other day until postnatal day 15 (total of eight doses). Before weaning, serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) remained at low levels during OP exposure, although the serum FSH peak and the high LH level were obvious in the controls. Histologically, inhibition of uterine gland genesis was apparent. The day of vaginal opening was about 4 days earlier in OP-treated animals than in controls. Persistent estrus was consistently observed in OP-treated animals. Atrophic and polycystic ovaries without corpora lutea showed anovulation. In the endometrium, cell-proliferative activity and cell-death were increased and decreased, respectively, and expression of estrogen receptor alpha mRNA was apparent by in situ hybridization. Unexpectedly, endometrial hyperplasias appeared at 8 weeks of age. After ovariectomy, vaginal smears immediately became of castration type and the uterus was atrophied. These results suggested that neonatal exposure to a high dose of OP alters developmental hormonal secretion presumably due to a hypothalamo-pituitary-ovarian disorder, with accelerated vaginal opening, subsequent persistent estrus, and uterine endometrial hyperplasia. The changes in the uterus and vagina are ovary-dependent.

Tissue-specific expression of messenger ribonucleic acids for insulin-like growth factors and insulin-like growth factor-binding proteins during perinatal development of the rat uterus

Insulin-like growth factor (IGF)-I and IGF-II play a number of important roles in growth and differentiation, and IGF-binding proteins (IGFBPs) modulate IGF biological activity. IGF-I has been shown previously to be essential for normal uterine development. Therefore, we used in situ hybridization assays to characterize the unique tissue- and developmental stage-specific pattern of expression for each IGF and IGFBP gene in the rat uterus during perinatal development (gestational day [GD]-20 to postnatal day [PND]-24). IGF-I and IGFBP-1 mRNAs were expressed in all uterine tissues throughout this period. IGFBP-3 mRNA was not detectable at GD-20 but became detectable beginning at PND-5, and the signal intensity appeared to increase during stromal and muscle development. IGFBP-4 mRNA was abundant throughout perinatal development in the myometrium and in the stroma, particularly near the luminal epithelium. IGFBP-5 mRNA was abundantly expressed in myometrium throughout perinatal development. IGFBP-6 mRNA was detected throughout perinatal development in both the stroma and myometrium in a diffuse expression pattern. IGF-II and IGFBP-2 mRNAs were not detected in perinatal uteri. Our results suggest that coordinated temporal and spatial expression of IGF-I and its binding proteins (IGFBP-1,-3,-4,-5, and -6) could play important roles in perinatal rodent uterine development.

Environmental estrogens and reproductive health: a discussion of the human and environmental data

Estrogenic activity of certain xenobiotics is an established mechanism of toxicity that can impair reproductive function in adults of either sex, lead to irreversible abnormalities when administered during development, or cause cancer. The concern has been raised that exposure to ambient levels of estrogenic xenobiotics may be having widespread adverse effects on reproductive health of humans and wildlife. The purpose of this review is to evaluate (a) the nature of the evidence supporting this concern, and (b) the adequacy of toxicity screening to detect, and risk assessment procedures to establish safe levels for, agents acting by this mechanism. Observations such as adverse developmental effects after maternal exposure to therapeutic levels of the potent estrogen diethylstilbestrol or male fertility problems after exposure to high levels of the weak estrogen chlordecone clearly demonstrate that estrogenicity is active as a toxic mechanism in humans. High level exposures to estrogenic compounds have also been shown to affect specific wildlife populations. However, there is little direct evidence to indicate that exposures to ambient levels of estrogenic xenobiotics are affecting reproductive health. Reports of historical trends showing decreasing reproductive capacity (e.g., decreased sperm production over the last 50 years) are either inconsistent with other data or have significant methodologic inadequacies that hinder interpretation. More reliable historical trend data show an increase in breast cancer rate, but the most comprehensive epidemiology study to data failed to show an association between exposure to persistent, estrogenic organochlorine compounds and breast cancer. Clearly, more work needs to be done to characterize historical trends in humans and background incidence of abnormalities in wildlife populations, and to test hypotheses about ambient exposure to environmental contaminants and toxic effects, before conclusions can be reached about the extent or possible causes of adverse effects. It is unlikely that current lab animal testing protocols are failing to detect agents with estrogenic activity, as a wide array of estrogen-responsive endpoints are measured in standard testing batteries. Routine testing for aquatic and wildlife toxicity is more limited in this respect, and work should be done to assess the validity of applying mammalian toxicology data for submammalian hazard identification. Current risk assessment methods appear to be valid for estrogenic agents, although the database for evaluating this is limited. In conclusion, estrogenicity is an important mechanism of reproductive and developmental toxicity; however, there is little evidence at this point that low level exposures constitute a human or ecologic health risk. Given the potential consequences of an undetected risk, more research is needed to investigate associations between exposures and effects, both in people and animals, and a number of research questions are identified herein. The lack of evidence demonstrating widespread xenobiotic-induced estrogenic risk suggests that far-reaching policy decisions can await these research findings.

Tissue distribution of three members of the murine protein disulfide isomerase (PDI) family

The distribution of PDI, ERp61 and ERp72, members of the protein disulfide isomerase (PDI) family of endoplasmic reticulum (ER) proteins, was determined in various murine tissues. Relative amounts of mRNA were measured using a quantitative reverse transcription-polymerase chain reaction (RT-PCR) method. Protein levels were determined from Western blots. In most tissues, protein levels paralleled the amount of mRNA for each PDI family member. The tissue distribution of the PDI and ERp72 mRNAs was similar, although ERp72 was not as abundant as PDI in the tissues. The tissue distribution of the ERp61 mRNA was significantly different from the two other family members. To help define potential hormonal or maturational differences in the regulation of expression of PDI family members, mRNA was measured in the frontal cortex, liver, pituitary gland and uterus at timed intervals during postnatal maturation. Except in the pituitary gland, the mRNA levels at 10 days and 22 days after birth were essentially identical to those in the adult. The ERp61 and ERp72 mRNAs were present at 2- to 3-fold higher levels in the pituitary glands of the 10- and 22-day-old mice, than in the adult mice. In addition, the pituitary gland PDI mRNA was 2- to 3-fold higher in 10-day-old mice than in adults. In general, levels of PDI family members were higher in secretory tissues than in other tissues in both immature and adult mice.

Effect of estrogen on ontogenic expression of progesterone and estrogen receptors in rat uterus

The ontogenic expression of progesterone and estrogen receptors (PR and ER) and effect of estrogen on these receptors were investigated immunohistochemically in rat uterus from the day of birth ( = 0 day) to 30 days of age. Uterine epithelial and stromal cells showed a negative PR immunoreaction at 0 day. The PR in the epithelial cell nuclei appeared by 5 days, while the stromal cells showed a negative PR reaction until 12 days. The staining of the stromal cells appeared from 12 to 15 days. In both the epithelial and stromal cells, the initiation of the PR appearance was not affected by ovariectomy performed at 0 day or 5 days prior to the appearance of PR in the epithelial and stromal cells. Estrogen injections from 0 day failed to initiate the appearance of PR in the epithelial cells, regardless of doses of estradiol-17 beta (0.1, 1 and 10 micrograms daily), but induced PR in the stromal cells. The staining of ER appeared at 5 days in the epithelial cells and at 1 day in the stromal cells, respectively. ER appeared after 2-3 daily injections of estrogen from 0 day depending upon the doses. These results suggest that steroid hormones secreted from neonatal ovary do not play any important role in ontogenic expression of PR during the postnatal uterine maturation.

Growth of separated and recombined neonatal rat uterine luminal epithelium and stroma on extracellular matrix: effects of in vivo tamoxifen exposure

We have developed a system for serum-free culture of separated uterine epithelium and stroma from 11-day-old rats recombined on extracellular matrix extracted from Englebreth-Holm-Swarm tumors. Epithelium grew and, after 2 days in culture, developed into luminal epithelial spheres (LES) surrounding a fluid-filled lumen. Individual LES cells maintained epithelial cell characteristics such as basally located nuclei, apical microvilli (oriented toward the lumen), lateral membranes with interdigitations and desmosomes, secretory Golgi complexes, and abundant mitochondria and rough endoplasmic reticulum. Secretory vesicles were ubiquitous throughout the luminal fluid. Addition of 17 beta-estradiol to the growth medium increased the number and longevity of the LES. Prior exposure of uteri to tamoxifen via s.c. injection in vivo on postnatal Days 1 to 5 reduced or completely inhibited formation of LES in vitro. These effects occurred regardless of whether the stromal or epithelial component of the recombinant tissue was exposed to tamoxifen. These data suggest a directive property of neonatal stroma in culture resulting in the formation of highly secretory spherical epithelial structures completely enclosing a lumen. LES formation is responsive to both estrogen (positive response) and antiestrogen (negative response).

Effects of estradiol valerate on the uterus of the musk shrew (Suncus murinus L.)

The effects of exogenous estradiol valerate on some uterine characteristics of the musk shrew were investigated. Treatment with the steroid for either 1 day or 7 days did not noticeably alter luminal epithelial cell height, endometrial gland epithelial cell height or diameter, or number of endometrial glands. The reciprocal values of cell density of circular muscle and deep endometrial layers and endometrium-to-myometrium ratio of the uterus increased significantly in response to 7 days of steroid administration. After 1 day of steroid treatment the numbers of mast cells in different layers of the uterus (i.e., meso-, myo-, and endometrium) were unchanged, but after 7 days there were significant increases in the number of mast cells in meso- and myometria. The number of eosinophils in all three layers of the uterus increased significantly in response to the treatment of estradiol for 1 day or for 7 days. The increase was greater in the 7-day group. Neither uterine DNA nor RNA contents changed following administration of the steroid for either group, although protein content was elevated significantly in the 7-day group. Estradiol administration thus evokes small but subtle changes in the uterus of the musk shrew.

Long-term effects of postnatal exposure to diethylstilbestrol on uterine estrogen receptor and growth

Diethylstilbestrol (DES) treatment of female rats on postnatal days (PND) 1-5 reduces uterine growth, estrogen receptor (ER) level and gland number by PND 25, while daily DES treatment on PND 1-25 increases uterine growth 4-fold, further reduces ER level and completely suppresses gland formation. We now report the persistence of these effects in adults. By PND 60, uterine weight was 70% of controls in rats injected with DES on PND 1-5 but only 10% of controls in rats injected PND 1-10 or longer. In fact, uterine weights were the same on PND 10 and 60. Uterine gland numbers were reduced to 30% of controls in all DES-treated rats regardless of exposure length; however, luminal and glandular epithelial cell heights were reduced to less than 50 and 70%, respectively, of controls when DES was given on PND 1-25 but not when given on PND 1-5. Ovariectomy 7 days prior to sacrifice on PND 60 reduced uterine weight in controls by 67% and in rats injected with DES on PND 1-5 by 53%, but had no effect in rats injected with DES on PND 1-10. DES exposure at either PND 1-5 or 1-10 lowered ER levels by 35-50% at both 60 and 90 days. Treatment with a high dose of estradiol (E2) 1 week before sacrifice significantly down-regulated ER to the same concentration in all treatment groups at PND 60 and 90. Following E2 treatment, all groups also showed increased uterine weight at PND 60 and 90. These data show there is a short period of development (PND 5-10) in which further DES exposure indirectly inhibits uterine growth.

Growth of neonatal rat uterine luminal epithelium on extracellular matrix

We have developed a tissue culture system using an extract of basement membrane (extracellular matrix) which promotes the in vitro growth and development of uterine luminal epithelium from the 5-day-old rat. Uterine luminal epithelium, free of stroma, was obtained as short tubes by trypsinization of uterine segments followed by mechanical separation. Epithelial segments were grown in a serum-free medium on culture dishes coated with an extracellular matrix. After 2 days, rapid cell growth resulted in monolayer cultures, which subsequently formed organoid structures similar to differentiated uterine glands present in uterine tissue taken from older rats. Electron microscopy of cultures revealed columnar cells with basally located nuclei, apical microvilli, lateral membranes with interdigitations, desmosomes, and secretory Golgi complexes, all features found in functioning uterine epithelium in vivo. This model will allow the in vitro investigation of the development of uterine epithelium-specific functions free of the influence of stromal cell factors.

Protein secretions in mouse uterus after methoxychlor or estradiol exposure

Four-month-old, ovariectomized mice were treated with 14 daily ip injections of either 10.0 micrograms of 17 beta-estradiol or 1.0 mg technical grade methoxychlor. Uterine luminal proteins were radiolabeled with 35S-methionine and run on 2-dimensional electrophoresis gels. The influence of methoxychlor or estradiol was compared to untreated controls by examining reproductive tract weights, uterine histology, and the patterns of uterine protein secretions. The data indicate that the stimulation of the uterus in ovariectomized, adult mice by methoxychlor is indistinguishable from that caused by estradiol. Both substances alter reproductive tract weights, promote cellular hypertrophy, stimulate uterine development, and induce the secretion of comparable levels of incorporation of methionine into a large number of proteins. The data further indicate that the alterations in gene expression promoted by estradiol in terms of secreted proteins appear to be qualitatively similar to those caused by the pesticide methoxychlor.

Histologic, morphometric, and immunocytochemical analysis of myometrial development in rats and mice: II. Effects of DES on development

The effects of diethylstilbestrol (DES) treatment on myometrial development from the prenatal to adult period were examined in rats and mice by histologic and immunocytochemical methods using anti-actin, -vimentin, and -laminin to assess cytodifferentiation of smooth muscle and fibroblastic cells, and by morphometric procedures to assess quantitatively the effect of DES on the expression of cellular orientation in the emerging inner circular myometrial layer. Neonatal rats and mice were treated with DES from day 0 (day of birth) to day 2 with dosages known to perturb myometrial development. Neonatal treatment with DES increased the degree of circular orientation within the uterine mesenchyme, an effect detectable following as little as 24 hr of DES treatment. This effect on spatial organization of the mesenchyme was followed by an increase in the thickness of the actin-positive middle layer (prospective circular myometrium) of uterine mesenchyme during days 3-15; from day 15 onward, however, the circular myometrial layer began to fragment into irregular bundles of smooth muscle, and the longitudinal myometrial layer became thinner and more irregularly organized than controls. Vimentin localization in rats treated with DES neonatally was more intense than in controls within the circularly orientated uterine mesenchyme at 5 days. By 60 days the circular and longitudinal myometrial layers of DES-treated animals showed strands and bundles of vimentin-positive cells, which were not present in controls. Both rats and mice show comparable effects of DES treatment.

Uterine abnormalities in rats exposed neonatally to diethylstilbestrol, ethynylestradiol, or clomiphene citrate

The toxicity of the synthetic estrogens diethylstilbestrol (DES), and ethynylestradiol (EE), and the antiestrogen clomiphene citrate (CC) was evaluated by assessing postnatal uterine growth and development prior to the onset of puberty in the rat. Both DES and EE, administered during the neonatal period (postnatal days 1-5), initially increased uterine weight and luminal epithelium hypertrophy. However, uterine weight declined in both DES- and EE-treated animals and fell below controls beyond day 11. Luminal epithelium stimulation generally paralleled uterine weight changes. Precocious development of uterine glands occurred after estrogenization (compared to untreated controls), but subsequently gland numbers were approximately 60% of control levels. Neonatal CC exposure induced only slight uterine weight gain but caused prolonged luminal epithelium hypertrophy and inhibited uterine gland genesis. Luminal epithelium hypertrophy appears to be a useful measure of antiestrogen activity. These data demonstrate the toxicity of DES and EE as assessed by altered prepubertal uterine gland development. Additionally, the inhibition of uterine gland genesis after neonatal CC exposure occurs in conjunction with prolonged luminal epithelium hypertrophy.

Alterations in developing rat uterine cell populations after neonatal exposure to estrogens and antiestrogens

Exposure of rats to either estrogens or antiestrogens during early postnatal development reduces subsequent uterine growth as measured by uterine weight. However, individual uterine cell types respond differently to these agents and uterine weight alone cannot discern subtle or even large alterations in individual cell populations. Using a computerized planimetric technique, we estimated the prepubertal growth of the uterine luminal epithelium, endometrial stroma, glands, and circular and longitudinal muscle after exposure of neonatal rats (postnatal days 1-5) to the estrogens 17 beta-estradiol (E2), diethylstilbestrol (DES), or ethynylestradiol (EE), and the antiestrogens tamoxifen or clomiphene citrate. On postnatal day 26, the cross-sectional areas of the luminal epithelium, endometrial stroma, and circular muscle were reduced after estrogen exposure, compared to untreated controls, while longitudinal muscle cross-sectional area was not affected. Since cell densities (cell number/unit area) were increased, these estrogen-induced area reductions demonstrate a decrease in cell size. Total cell numbers, estimated as the product of cell type areas and their respective cell densities, were also reduced by neonatal estrogen exposure. The synthetic estrogens DES and EE were more potent than E2 with respect to reduction of uterine growth. Neonatal antiestrogen exposure caused large area reductions only in the uterine glands and luminal epithelium. Little change in cell density occurred in any cell population exposed to antiestrogen. These data demonstrate that the decreased uterine growth resulting from estrogen exposure during early postnatal development is a consequence of combined hypotrophy and hypoplasia in all cell types except longitudinal muscle while antiestrogen-induced morphological alterations were limited to hypoplasia having epithelial cell specificity.

Postnatal uterine development in the rat: estrogen and antiestrogen effects on luminal epithelium

We examined the effects of the synthetic estrogens, diethylstilbestrol (DES) and ethynylestradiol (EE), and the triphenylethylene antiestrogen, clomiphene citrate (CC), on uterine growth and development in the rat. These compounds, unlike estradiol, do not bind significantly to rat serum alphafetoprotein (AFP). Administration of DES or EE during the period of normal uterine gland genesis (postnatal days 10-14) induced luminal epithelium hypertrophy and increased uterine wet weight. The durations of these responses were dose-related. By day 26, luminal epithelium cell numbers were significantly depressed, compared to controls. Uterine gland development was delayed 6 to 9 days, depending upon estrogen dose, and the numbers of uterine glands ultimately achieved were generally less than in untreated control animals. While a daily dose of 0.1 micrograms CC/rat did not alter uterine development, 10 micrograms CC/rat caused prolonged luminal epithelium hypertrophy and inhibited uterine gland genesis without inducing the large increases in uterine weight or the decreases in luminal epithelium cell number seen after estrogen exposure. The number of stromal cells was significantly increased on day 26 after CC exposure. Together with previous studies, these data demonstrate the greater potency and developmental stage specificity of non-AFP-bound estrogens with respect to altering uterine gland development. In addition, these data suggest that the disruptive influence of antiestrogens on gland genesis may be mediated through an indirect influence on the uterine stroma.

Effects of postnatal DES treatment on uterine growth, development, and estrogen receptor levels

The neonatal rodent appears to be an appropriate animal model for estrogen toxicity in the developing reproductive tract. Newborn rats were treated with diethylstilbestrol (DES) at human therapeutic doses (approx 1 mg/kg) during two ontogenetic periods (postnatal days 1-5 and 1-25). Treatment on days 1-5 doubled uterine wt by day 5; however, these uteri failed to grow after discontinuation of DES treatment. In contrast, uterine wt was 4-fold higher and DNA content was 2-fold higher than controls on days 10-25 with continued DES treatment. Total uterine estrogen receptor levels, depressed 60% by day 5 of DES treatment, partially recovered after discontinuation of DES treatment but remained 25% below controls on day 25. Receptor levels following DES on days 1-25 decreased to about 15% of the controls by day 15. Short-term DES treatment approximately halved uterine gland content while continued treatment almost completely inhibited gland appearance. DES effects on glands appear related to continued hypertrophy of the luminal epithelium, from which uterine glands are derived. Subsequent failure of uterine growth caused by DES treatment on days 1-5 is similar to clinical findings of hypoplastic uteri in DES-treated patients. Disruption of the normal ontogenetic patterns of estrogen receptor by DES may be involved. These data demonstrate abnormal patterns of growth, estrogen receptor levels and morphogenesis in uteri of rats treated postnatally with DES.

Teratogenic effects of clomiphene, tamoxifen, and diethylstilbestrol on the developing human female genital tract

The potential estrogenicity and teratogenicity of triphenylethylene antiestrogens were examined in 54 genital tracts isolated from 4- to 19-week-old human female fetuses and grown for 1 to 2 months in untreated athymic nude mice or host mice treated by subcutaneous pellet with the antiestrogens clomiphene and tamoxifen or the synthetic estrogen diethylstilbestrol (DES). In specimens grown to a gestational age equivalent of 15 weeks or less, the vagina and urogenital sinus were lined by an immature squamous epithelium, which were similar in both drug-treated and untreated specimens. Proliferation and maturation of the squamous vaginal epithelium were observed in specimens treated with clomiphene, tamoxifen, or DES only when grown to a gestational age equivalent of 16 weeks or more. Formation of endometrial and cervical glands proceeded in 87 per cent (13 of 15) of control specimens grown to a gestational age equivalent of 13 weeks or more in untreated hosts. By contrast, age-matched drug-treated specimens contained glands in only 44 per cent (12 of 27) of specimens. In the developing uterine corpus of untreated controls, the uterine mesenchyme segregated into inner (endometrial stroma) and outer (myometrial) layers; whereas in drug-treated specimens, condensation and segregation of the mesenchyme were greatly impaired. The fallopian tube was also affected by clomiphene and tamoxifen (and to a lesser extent by DES) in that its epithelium was hyperplastic and disorganized. The complex mucosal plications characteristic of the fallopian tube were also distorted in drug-treated specimens. These results emphasize the heretofore unrecognized estrogenicity and potential teratogenicity of triphenylethylene antiestrogens on the developing human genital tract and emphasize the need for caution to prevent inadvertent exposure of the developing fetus to these compounds.

Gonadotropin- and estrogen-induced increase of peripheral-type benzodiazepine binding sites in the hypophyseal-genital axis of rats

Peripheral-type benzodiazepine binding sites (PBS) were demonstrated in the cell membranes of various organs (ovary, uterus, oviduct, pituitary and kidney) of mature and immature female rats by using the PBS-specific ligand [3H]PK 11195. The equilibrium dissociation constants of [3H]PK 11195 for PBS in mature rats ranged from 3 to 4 nM. The specific binding of [3H]PK 11195 (2 nM) in the hypophyseal-genital axis of immature (19-27 days old) female rats was found to be significantly increased in the ovary and uterus, concurrently with the increase in age. Administration of pregnant mare serum gonadotropin or diethylstilbestrol to immature rats increased the density of PBS in the ovary and uterus 2- to 3-fold but no change was found in the kidney. The affinity of [3H]PK 11195 to these tissues did not change following hormonal treatment. These results suggest that gonadotropin and estrogen are involved in the induction of PBS in the organs of the hypophyseal-genital axis in female rats.

Dissociation of estrogen-induced uterine growth and ornithine decarboxylase activity in the postnatal rat

Estrogens are teratogens and developmental carcinogens in several species. We have used uterine growth to quantitate the potency of three estrogens [estradiol (E2), diethylstilbestrol (DES), ethynylestradiol (EE2)] during four postnatal periods (days 1-5, 10-14, 20-24, and 60-64) in the rat. Alphafetoprotein (AFP), present at high levels in neonatal serum, is thought to regulate estrogen bioavailability. Association constants for DES and EE2 were 2.7% and 4.9% of that for E2 binding to AFP, determined in a batch Sephadex equilibrium binding assay. On days 1-5, DES and EE2 were about 80-fold more potent than E2 in increasing uterine weight. As AFP levels fell, potency differences between E2 and the synthetic estrogens decreased. In the adult, which essentially lacks AFP, the three estrogens were nearly equipotent. These data are consistent with AFP regulation of estrogen potency. On days 10-14, uterine growth was less sensitive than at other ages to all three estrogens, perhaps related to uterine differentiation and/or the high endogenous serum E2 levels reported at this age. However, when we examined another uterine estrogen response, ornithine decarboxylase (ODC) induction at 6 h following estrogen injection, all three hormones were about equipotent in both neonatal and adult animals. This apparently AFP-independent event shows dissociation of ODC induction and uterine growth, which could be due to separate mechanisms for hormone entry to target tissue or subsequent intracellular events.

Occurrence of genital tract abnormalities and bladder hernia in female mice exposed neonatally to tamoxifen

Three groups of female C57BL/Tw mice given 5 daily injections of 2, 20 or 100 micrograms tamoxifen (Tx) starting on the day of birth were killed at 35 and 150 days of age. About a half of the mice killed at 150 days had been ovariectomized at 90 days. Uterine hypoplasia, myometrial involution and suppression of the uterine-gland genesis were found in the 2 age-groups of Tx-treated mice. Vaginal hypoplasia and hypospadia were common abnormalities in 150-day-old Tx-treated mice. Vaginal adenosis was encountered in 35-day-old mice treated neonatally with 20 or 100 micrograms Tx, but not in 150-day-old group. Permanent proliferation of vaginal epithelium was not induced by Tx. More than 80% of oocytes in small follicles were degenerated in Tx-exposed mice at 150 days, but not so in those at 35 days. Ovaries of neonatally Tx-exposed mice lacking corpora lutea made no luteinizing response to human chorionic gonadotropin injected prepubertally. Urinary-bladder hernia with or without caecum hernia frequently occurred in 150-day-old mice given 20 or 100 micrograms Tx. The present study revealed that neonatally administered Tx causes various abnormalities in gonad and genito-urinary tract of female C57BL/Tw mice.