Long term effects of perinatal injection of estrogen and progesterone on the morphological and biochemical development of the mammary gland

Effects of Neonatal Exposure to Diethylstilbestrol, Tamoxifen, and Toremifene on the BALB/c Mouse Mammary Gland1

In this study, we compared the long-term effects of neonatal exposure to diethylstilbestrol (DES, 0.0125-50 microg), tamoxifen (TAM, 0.0125-50 microg), and toremifene (TOR, 53 microg) on mammary gland development and differentiation. Allometric growth of the mammary ducts was stimulated by neonatal DES exposure (12.5 microg) and impaired by exposure to TAM (25 microg). Neonatal treatment with high doses of DES resulted in mammary ducts that displayed extensive dilatation and precocious lactogenesis in postpubertal, nulliparous females. Initiation of this precocious differentiation coincided with the absence of corpora lutea, increased levels of serum prolactin (PRL), and the induction of Prl mRNA expression within the mammary glands. Neonatal exposure to 1.25 microg TAM increased alveolar development in postpubertal, nulliparous females similar to that recorded in females treated with low doses of DES. Lower doses of TAM did not affect alveolar development, whereas branching morphogenesis and alveolar development were impaired by higher doses. Increased alveolar development in females exposed to 1.25 microg TAM was associated with elevated serum progesterone (P) and increased alveolar development in response to exogenous P. Taken together, our findings demonstrate that neonatal exposure to both DES and TAM exerts long-lasting effects on the proliferation and differentiation of the mammary glands in female BALB/c, primarily as the result of endocrine disruption.

Acceleration of mammary neoplasia in aromatase transgenic mice by 7,12-dimethylbenz[a]anthracene

Our studies using the aromatase transgenic mice model have shown that early exposure of mammary epithelium to in situ estrogen as a result of overexpression of aromatase predispose mammary tissue to preneoplastic changes. Here, we hypothesize that the preneoplastic changes induced by mammary estrogen in aromatase transgenic females may be susceptible to environmental carcinogens like 7,12-dimethylbenz[a]anthracene (DMBA), and may result in the acceleration and/or increase in the incidence of breast cancer. Results presented in this study show that tumors appeared in 25% of the mice that were treated with DMBA and all treated transgenic animals had microscopic evidence of neoplastic progression. Control non-transgenic females did not have significant changes even after treatment with DMBA. Consistent with increased neoplastic changes in DMBA-treated aromatase mice, we have seen an increase in the expression of genes involved in cell proliferation and cell cycle. We have also seen changes in the expression of oxidative stress markers and changes in estrogen-mediated growth factors. These studies indicate that more than one event is required for tumor formation, and that early estrogen exposure leading to preneoplastic changes in the mammary epithelial cells increases susceptibility to environmental carcinogens that may result in acceleration and/or an increase in the incidence of breast cancer.

The replacement of oestradiol and progesterone in very premature infants

The idea of replacing 17beta-oestradiol (E2) and progesterone (P) in preterm infants is based on the observation that during pregnancy E2 and P plasma concentrations rise in the mother and the fetus by a factor of 100. Disruption of the placental supply of these hormones is a physiological event for an infant delivered at term. A preterm infant is deprived from this supply at an earlier developmental stage. In vitro and in vivo data are discussed, and they highlights the potential benefit of E2 and P on the development of different organ systems. The postnatal replacement of E2 and P has the aim of maintaining in utero plasma concentrations. In the first randomized clinical study in 30 extremely preterm infants, E2 and P were replaced postnatally for a total of 6 weeks. With a median intravenous replacement of 8.4 micromol/kg/day of E2 (4.2-22.9) and 67.4 micromol/kg/day of P (35.7-87.0), plasma levels of E2 and P were maintained within the intrauterine reference values of 7.3-22.0 nmol/L and 0.95-1.9 micromol/L, respectively. Three- to sixfold higher dosages were needed via the transepidermal route. Trends towards an improved postnatal bone mineral accretion and a reduced incidence of chronic lung disease were found. Further studies are warranted to clarify the potentially important role of E2 and P for the postnatal development of an extremely preterm infant.

17Beta-estradiol and progesterone supplementation in extremely low-birth-weight infants

During pregnancy, 17beta-estradiol (E2) and progesterone (P) plasma concentrations increase up to 100-fold. The fetus is exposed to these increasing amounts of E2 and P. Within 1 d after delivery, E2 and P concentrations fall to nonpregnancy concentrations in the mother and the infant. Extremely premature infants are cut off from the placental supply of E2 and P at a very early developmental stage, and therefore they suffer from this deprivation for a longer period than infants born at term. Nothing is known about the consequences of this deprivation. The purpose of this study was to investigate how intrauterine concentrations of E2 and P could be maintained after birth. In 13 infants with a median gestational age of 26.4 wk (24.1-28.7), a phospholipid-stabilized soybean oil emulsion available for parenteral nutrition that contains different amounts of E2 and P was continuously administered, starting within the first postnatal hours. The supplementation was continued as long as venous access was indicated but not longer than 6 wk (median 20 d, 12-44). To maintain intrauterine plasma concentrations of 2000-6000 pg/mL E2 and 300-600 ng/mL P, 2.30 mg x kg(-1) x d(-1) E2 (1.13-3.42 mg x kg(-1) x d(-1)) and 21.20 mg x kg(-1) x d(-1) P (11.23-27.36 mg x kg(-1) x d(-1)) were needed. We conclude that supplementation of E2 and P to maintain intrauterine concentrations in extremely premature infants is possible intravenously. The infants in this study are enrolled in a randomized, controlled pilot study to evaluate the potential benefits of E2 and P supplementation.

Altered mammary responsiveness to estradiol and progesterone in mice exposed neonatally to diethylstilbestrol

Mammary glands from ovariectomised neonatally diethylstilbestrol (DES)-exposed (0.1 microgram daily for the first 5 days of life) mice seem morphologically indistinguishable from those of ovariectomised controls. However, administration of exogenous hormones reveals a differential response. In DES-exposed mice, estrogen implantation resulted in greater incidence of dilated ducts along with greater incidence of dilated ducts along with greater incidence and severity of terminal ductal hyperplasia and greater severity of cystic alveolar adenosis; combined estrogen and progestin treatment resulted in greater severity of terminal duct hyperplasia and less alveolar formation, and progestin treatment resulted in lower incidence and degree of lateral budding. Thus, mammary sensitivity to sex steroids is altered by early exposure of mice to DES.

Effects of perinatal exposure to a synthetic estrogen and progestin on mammary tumorigenesis in mice

The effects of perinatal exposure to synthetic estrogens and progestins on mammary tumorigenesis were studied in female C3H/HeN/MTV + mice. Mice were treated neonatally with 0.001 microgram/day diethylstilbestrol (DES), with 15 micrograms/day 17 alpha-hydroxyprogesterone caproate (HPC), or with oil on days 1-5 of life (birth = day 1). As adults, neonatally hormone-treated mice received long-term treatment with a synthetic estrogen and progestin combination or vehicle. Animals were palpated weekly for mammary gland tumors. The effect of treatment on the probability of tumor development was examined. Neonatal treatment with a low dose of DES increased the probability of mammary-gland tumor formation, whereas neonatal treatment with HPC had a slightly protective effect on tumorigenesis. Subsequent treatment of adult mice with synthetic steroids did not affect mammary gland tumorigenesis in neonatally DES-treated or oil-treated animals. There was a significant interaction between the effect of neonatal HPC treatment and subsequent steroid treatment on mammary tumorigenesis but examination of the data indicated that this interaction was due to the protective effect of HPC in the absence of subsequent exposure to synthetic steroids and the probability of tumor appearance in mice treated with both HPC and synthetic steroids as adults did not differ from that of neonatally oil-treated controls.

Neonatal exposure to DES in BALB/c male mice: effects on pituitary-gonadal function

Neonatal male BALB/c mice were injected with diethylstilbestrol (DES), estradiol benzoate (E2B), testosterone propionate (TP), progesterone or DES, in combination with E2B, TP or progesterone and examined in adulthood. Body weight was reduced in males exposed to DES, TP or DES + TP, while testicular weight was reduced in animals injected with DES, E2B, TP, DES + TP or DES + progesterone. Exposure to DES and/or E2B also produced reproductive tract abnormalities and concomitant progesterone exposure did not further affect this parameter. Concomitant DES did not further alter the reduced plasma luteinizing hormone (LH) levels attributable to neonatal TP or E2B treatment. Plasma follicle-stimulating hormone (FSH) levels in intact males were increased by DES, DES + progesterone or progesterone alone. Assessment of the feedback effects of exogenous gonadal steroids on pituitary gonadotropin release in castrated adults indicated that injection of 125 micrograms TP further increased the already elevated post-castration levels of LH and FSH in mice neonatally exposed to progesterone. The increase in testosterone (T) concentration after intratesticular human chorionic gonadotropin (hCG) administration was significantly attenuated in mice neonatally exposed to DES plus E2B or to progesterone. Basal testicular T levels were significantly elevated in males exposed to DES, alone, or in combination with progesterone. Exposure to DES and TP increased hypothalamic serotonin (5-HT) levels in intact mice, while levels of 5-HT were lower after castration compared to controls. DES + E2B-treated mice had higher norepinephrine (NE) levels, and E2B-treated mice also had higher 5-HT levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth of mammary epithelial cells from neonatally sex hormone-exposed mice in serum-free collagen gel culture

Neonatal sex hormone treatments are known to cause an increase in mammary tumors in female mice with expressed mammary tumor virus (MTV). The growth of mammary epithelial cells from mice treated neonatally with sex hormones was studied in response to growth-stimulatory factors in a serum-free collagen gel culture system which sustains the growth of normal mammary epithelial cells. Animals were treated with hormones or oil-vehicle for the first 5 days after birth. Cells from control mice at 2 and 3 months of age showed a maximal growth response to insulin at 5-10 micrograms/ml and LiCl at 5-20 mM. Cells responded to epidermal growth factor at all concentrations used (1, 10 and 50 ng/ml). In contrast, mammary epithelial cells from mice treated neonatally with estrogen (estradiol and diethylstilbestrol (DES] showed a reduced growth response to the growth factors tested.