Glycolysis in the mouse uterus during the early post-implantation stages of pregnancy and the effects of acute doses of ethanol

The objective of this study was to assess the possibility that, in mice, alcohol interferes with uterine glycolysis to influence indirectly embryonal development. Glycolysis was found to be a major metabolic process in the mouse uterus and its pattern of activity changed during post-implantation pregnancy between days 5 and 9. This was evidenced by changes in glycolytic enzymes and intermediates, and in the capacity of endometrial preparations to consume oxygen and produce lactate during incubation in vitro. The intraperitoneal administration of ethanol at 3.0 and 6.0 gm/kg body weight, but not at 1.5 gm/kg body weight, on day 9 of pregnancy modified glycolysis in the uterus after 2 hours, resulting in significant changes in the rates of accumulation of glucose, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-diphosphate, and citrate. These effects were not mediated by changes in redox state, since the ratio of lactate to pyruvate remained unchanged after injection of ethanol. Citrate was considered to be a major factor involved both in the regulation of uterine glycolysis and in the ethanol-induced alterations in the levels of hexose phosphates. The elevated levels of uterine glucose registered after treatment with ethanol were related to an acceleration of glycogen degradation in the liver and not in the uterine endometrium. The results suggest that part of the adverse action that these doses of ethanol exert on embryonal development stems from indirect effects that involve uterine functions relating to the nurture of the conceptus via glycolysis.     

The effect of hypertonic solution on the wet weight and contractions of rat uterus and vas deferens

The role of propagated activity in the responses to agonist drugs was studied for the rat uterus and vas deferens. Hypertonic solutions were used to inhibit propagation of activity by shrinking cells. Tissue weight was used to indicate cell volume. Hypertonic solutions after 10 min caused weight loss and reduced the size of contractions in response to submaximal doses of drugs, to KCl, and to external electrical stimulation. Contractions in response to KCl and drugs were diminished to a similar degree in the vas deferens, but in the uterus, drug contractions were depressed much more. Prolonged action of hypertonic solution also differed for the two tissues. In the uterus, weight changes correlated with changes in size of the drug-induced contractions. Uterine contractions reduced in hypertonic solution could be increased by using supramaximal doses of drug. When stimulation was applied to one end of the uterus in a three compartment bath, propagation of spontaneous drug- and KCl-induced contraction occurred, but it was prevented by placing hypertonic solution in the center compartment. An increase of the KCl to 44 mM in the hypertonic solution restored propagation. These experiments yielded no evidence of propagated responses in the rat vas deferens. It was concluded that propagated activity plays a role in drug-induced contractions in the rat uterus but not in the rat vas deferens. Hyperpolarization of shrunken cells might be involved in inhibition of propagation by hypertonic solutions.     

Aromatase inhibition by R 83 842, the dextro isomer of R 76 713, in JEG-3 choriocarcinoma grown in ovariectomized nude mice

The effects of repeated (5 days) dosing with the non-steroidal aromatase inhibitor R 83 842 (the dextro isomer of R 76 713) on tumor aromatase and uterus weight in ovariectomized nude mice bearing JEG-3 tumors were examined. In animals bearing an androstenedione implant the presence of a JEG-3 tumor significantly increased uterus weight, proving that tumor aromatase indeed converted androgens to estrogens. Oral administration of R 76 713 (10 mg/kg) for 5 days reduced the increase in uterus weight by 84% in tumor bearing mice revealing true in vivo aromatase inhibition by R 76 713.

Experiments performed in the absence of exogenously added androgens gave similar results. Uterus weights in tumor bearing mice were significantly higher than in control mice. Oral administration of R 83 842 (5 mg/kg) for 5 days reduced uterus weight in the tumor bearing animals. Ex vivo aromatase measurements performed in JEG-3 tumors from these animals showed an aromatase inhibition of 93.9% in treated mice as compared to untreated mice. Five days oral treatment with R 83 842 dose-dependently lowered both aromatase activity and uterus weight. Doses of 5 and 0.5 mg/kg inhibited tumor aromatase by 94.1 and 74.7%, respectively, and reduced uterus weight. After a dose of 0.05 mg/kg aromatase activity and uterus weight were similar to those in the control group.     

The effects of melatonin and hypothyroidism on estradiol and gonadotropin levels in female Syrian hamsters

Since melatonin injections administered near the end of the daily photoperiod influence both gonadal and thyroid hormones in the female hamster, the present study was designed to compare the effects of melatonin and hypothyroidism on the reproductive system and to determine whether thyroid status influenced the action of melatonin on the regulation of the hormones of reproduction. The effects of daily melatonin injections were determined in control hamsters, in hamsters rendered hypothyroid with thiourea, and in hypothyroid hamsters receiving thyroxin (T4) hormone replacement. As previously reported, melatonin injections disrupted estrous cyclicity, disrupted the normal pattern of gonadotropin secretion, and resulted in atrophy of the uterus and vagina. These changes coincided with depressed serum and pituitary prolactin (PRL), and depressed levels of estradiol. The effects of melatonin on uterus, vagina, ovary, and on gonadotropin levels were not prevented by T4 replacement, with the exception of a melatonin-induced increase in serum follicle-stimulating hormone (FSH). This suggested that the cessation of estrous cyclicity was not primarily a result of thyroid deficiency. Hypothyroidism, however, like melatonin, resulted in a reduced number of developing and mature follicles and corpora lutea in the ovaries, and in reduced uterine weight. It also produced follicular atresia, reduced the circulating levels of estradiol, and resulted in reduced incidence of estrus smears. T4 replacement, for 2 weeks, prevented the decline in mature follicles and corpora lutea, reduced the extent of follicular atresia, increased circulating levels of estradiol, and increased uterine weight. PRL and luteinizing hormone (LH) data also provided evidence for antagonistic effects of melatonin and T4 in female hamsters. These data raise the question whether melatonin-induced changes in circulating levels of T4 play a role in the seasonal cycles of reproductive competence in the female hamster.     

Effect of estriol on the structure and organization of collagen in the lamina propria of the immature rat uterus.

Estradiol produces both hypertrophic and hyperplastic changes in the uterus, and these changes are associated with alterations in the structure of collagen in the lamina propria. Estriol induces only hypertrophic responses in the immature rat uterus; its effects on collagen structure were characterized in this study. Light micrographs of Masson's trichrome-stained sections revealed that the intensity of the collagen stain in the lamina propria of the rat uterus was profoundly reduced, relative to that in controls, 4 h after estriol (40 micrograms/kg) administration. These changes were not evident 24 h after estriol administration. In control uteri, transmission electron micrographs revealed that the collagen fibers surrounding stromal cells formed dense collections of bundles that were seen throughout the extracellular matrix, whereas in tissues exposed to estriol 4 h earlier, large regions of the extracellular spaces were devoid of collagen bundles. The 4-h changes in collagen were eliminated when animals were pretreated with actinomycin D (8 mg/kg) or cycloheximide (4 mg/kg). Dense collections of collagen bundles were present in tissues 24 h after estriol treatment, and their appearance was not altered by actinomycin D or cycloheximide treatment. Alterations in collagen 4 h after hormone administration appeared to be estrogen-specific since dexamethasone (600 micrograms/kg) and dihydrotestosterone (400 micrograms/kg) had no effect. These data provide evidence that the changes in collagen structure in the uterus are associated with events that function during the hypertrophic growth responses induced by estrogens.     

The effect of hypothyroidism on the female genital tract of gerbils (Meriones hurrianae jerdon).

The effects of hypothyroidism on the female genital tract of gerbils have been studied. Hypothyroidism was produced by (a) surgical ablation, and (b) pharmacological suppression of the gland. Hypothyroidism resulted in atrophic ovaries. Follivular development was severely arrested, with most of the follicles showing atresia. Distinct effects were produced upon the uterine physiology. Uterine regression was conspicuous in thyroidectomized females. Hypothyroidism resulted in a decreased RNA, protein, sialic acid and glycogen concentration of the uterus. Vaginal RNA, protein and sialic acid contents were low after thyroidectomy. The vaginal cytology showed a constant pattern of its cells, i.e. dioestrous. L-thyroxine treatment restores the biochemical changes of uterus and vagina to subnormal levels in thyroidectomized animals. It is concluded that hypothyroidism affected the weight, cytology and biochemistry of the female genital tract of gerbils.     

The effects of subnutrition on the components of the gravid uterus in the doe

The effects of subnutrition on the caprine fetus and the other products of pregnancy were investigated in does. Two groups of does were fed on rations calculated to provide 100 and 25% of their energy and protein requirements for maintenance from 19 days before mating until 60 days after mating. Estrus was synchronized in does using PGF(2x). Approximately 60 days after natural mating, pregnant does were slaughtered, and the products of pregnancy were measured. Fetuses from the feed-restricted group were significantly lighter (P<0.05), had shorter crown-rump length (P<0.05), and the uterus contained a smaller volume of fetal fluids (P<0.02). Curved crown-rump length tended to be shorter and fetal placental membranes and cotyledons tended to be lighter (P<0.1) in the feed-restricted group. No significant difference was found between the 2 groups in the head length, number of placentomes, and weight of empty uterus. The number of fetuses affected the number of placentomes (P<0.001), weight of empty uterus (P<0.001), mass of total fetal fluids (P<0.001) and weight of ovaries (P<0.05), but not fetal measurements. Gestation length was found to significantly (P<0.001) affect all the fetal measurements but none of the placental measurements except for the total weight of cotyledons (p<0.001). The results of the study demonstrated detrimental effects of underfeeding on the caprine fetus and placenta.     

Effect of tobacco smoke on the level of estrogens and DNA in the rat uterus

Tobacco smoke induced no changes in the rat uterus weight or in oestrus cycle but decreased estradiol (E2) concentration in the uterus tissue and increased and later decreased the proliferation index and percentage of the cells in the S-phase. The data obtained suggest a phasic character of changes in the reproductive system under the effect of tobacco smoke and corroborate the concept of the role of smoking in the shifting the type of hormonal carcinogenesis from promotional to genotoxic one.     

Changes in the levels of protein and steroid hormones in the plasma and steroid hormone receptors in the uterus of normal cycling guinea pigs

This study deals with the estrous cycle of guinea pigs in relation to sexual behavior, uterine weight, levels of gonadotropins, steroid hormones, and steroid hormone receptors in the uterus. The guinea pigs in this study showed cyclic changes in various reproductive functions broadly similar to other laboratory species studied. The increase in the uterine weight coincided with high concentration of steroid hormones (estradiol and progesterone) secreted during proestrus and estrus. The elevated levels of steroid hormone receptor concentrations in the uterus during these periods also confirm the role of these hormones. The rise in progesterone level from day 14 of the cycle was associated with lordosis and its related behavior. It was noted that the "estrus behavior" is the most accurate external marker for ovulation and sexual receptivity to males. It was also observed that there is an association between follicle-stimulating hormone and luteinizing hormone during the preovulatory period that was not demonstrated in previous studies.     

The role of the pituitary in modifications of the uterine secretion of spayed, oestradiol-primed rats

Tests performed on spayed, adult female estradiol-primed Ivanovas rats, with ligated uteri and normal pituitary function have shown that treatment with sexual steroids, including progesterone and testosterone, modifies uterine secretion. One half of the animals were hypophysectomized. In estradiol primed hypophysectomized controls, growth was retarded about 28%, the weight of the empty uterus reduced, and the quantity of uterine secretion diminished in comparison with the values for the nonhypophysectomized controls. In test rats treated with estradiol, gain in body weight was virtually arrested in the nonhypophysectomized rats and a reduction in weight was observed in both groups treated with the highest dose of estradiol tested (300 mcg/kg daily). In rats treated with progesterone, no significant differences were found between the two groups. In treated groups, a dose-related reduction in the weight of the empty uterus was found. Treatment caused a marked reduction in the quantity of the uterine secretion, the effect appearing greater in nonhypophysectomized rats. Increasing doses of progesterone produced a rapid rise in the viscosity of the uterine fluid, as well as a decrease in the pH of the uterine lumen. In both hypophysectomized and nonhypophysectomized rats, testosterone induced a dose-related increase in body weight, statistically significant only in animals with intact pituitaries treated with 100 mg/kg daily. The weight of the empty uterus also increased. The quantity of uterine fluid was reduced by testosterone only when it was given in massive doses to nonhypophysectomized rats. Doses of 100-300 mg/kg daily were needed to produce the same response as a dose of about 10 mg/kg daily of progesterone. In response to large doses, viscosity of secretion rose slightly and the pH of uterine lumen and secretion decreased. It may be concluded that the progestative modifications induced by progesterone in the uterus of spayed, estradiol-primed rats, including particularly changes in uterine secretion, are the effects of a peripheral mechanism not involving the pituitary. Testosterone appears to be an exception as far as the quantity and viscosity of uterine secretion are concerned, since modifications in these parameters are only observed in the presence of a functional pituitary body.     

Age dependency of estrogen responsiveness in the uterus and adipose tissue of aromatase-knockout (ArKO) mice

Aging is often associated with weight gain caused by metabolic changes including an increase of body fat. In this study we assessed the impact of age on estrogen responsiveness in the uterus and adipose tissue (AT) in aromatase-knockout (ArKO) mice. ArKO mice at the age of three or twelve months respectively were treated s.c. with vehicle, E(2) (10 μg/kg BW/d) or genistein (15 mg/kg BW/d) for three days. In the ArKO mouse model we were able to demonstrate that estrogen treatment resulted in an age specific response pattern both on a physiological and molecular level. Assessment of basal gene expression levels revealed significant age dependent differences only for elevated Esr1 levels in the uterus and leptin levels in infrarenal fat as well as lower levels of Pparg in the gonadal fat tissue. Investigating age dependency of estrogen responsiveness we were able to show that the E(2) and genistein resulted in age related pattern of regulation of expression of Esr1 and Lep in infrarenal and gonadal AT as well as the uterine expression of Pgr, Ltf and Pparg. In conclusion, evidence is provided that aging has an impact on the effectiveness of estrogen regulated processes in uterus and AT of ArKO mice. It remains to be elucidated whether or not this is associated with weight gain caused by an increase in body fat mass.     

不同干预方法对去卵巢骨质疏松大鼠子宫GSK-3β蛋白表达的影响

目的观察全身垂直振动、跑台运动和金雀异黄酮对去卵巢骨质疏松大鼠子宫重量指数和组织形态学以及糖原合成激酶3β（GSK-3β）蛋白表达的影响。方法将72只3月龄雌性SD大鼠按体重分层后随机分为假手术组（12只）和去卵巢组（60只）。去卵巢10周时,将去卵巢组大鼠按体重分层后又随机分为去卵巢组、振动组、跑台组、金雀异黄酮组和雌激素组（每组8~10只）,并开始进行不同干预处理。干预处理8周时,于末次处理结束36~48h内,腹主动脉取血处死各组大鼠,用电子天平称量大鼠子宫的重量,用HE染色方法观察子宫形态学的变化,用Western blot方法检测子宫GSK-3β和P-GSK-3β蛋白表达的变化。结果与去卵巢组比较,雌激素组大鼠子宫重量指数显著增加,而振动组、跑台组、金雀异黄酮组大鼠子宫重量指数均无显著变化;与去卵巢组比较,雌激素组、跑台组和振动组大鼠子宫P-GSK-3β/GSK-3β蛋白的比值均显著增加,而金雀异黄酮组无显著变化。结论全身垂直振动和跑台运动均能刺激去卵巢骨质疏松大鼠子宫GSK-3β蛋白的磷酸化,而金雀异黄酮无此效应。     

Maternal obesity modulates both the renin–angiotensin system in mice dams and fetal adiposity

Obesity is a chronic multifactorial disease and is currently a public health problem. Maternal obesity during pregnancy is more dangerous as it impairs the health of the mother and future generations. Obesity leads to several metabolic disorders. Since white adipose tissue is an endocrine tissue, obesity often leads to disordered secretion of inflammatory, glycemic, lipid and renin–angiotensin system (RAS) components. The RAS represents a link between obesity and its metabolic consequences. Therefore, our goal was to evaluate the possible changes caused by a high-fat diet in RAS-related receptor expression in the uterus and placenta of pregnant mice and determine the underlying effects of these changes in the fetuses’ body composition. Breeding groups were formed after obesity induction by high-fat (HF) diet. Dams and fetuses were euthanized on the 19th day of the gestational period. The HF diet effectively induced obesity, glucose intolerance and insulin resistance in mice. Fetuses born from HF dams showed increased body weight and adiposity. Both results were accompanied by increased AT₁R expression in placenta and uterus together with increased angiotensin-converting enzyme expression in the uterus and a decreased expression of MAS1 in placenta of HF dams. These results suggest a link between RAS, maternal obesity induced by HF diet and the fetuses’ body adiposity. This new path now can be more thoroughly explored.     

Intracellular relationships of the oestrogen receptor in the rat uterus and hypothalamus during the oestrous cycle.

Simultaneous measurements were made of the specific oestrogen receptor in the nuclear and cytosol fractions prepared from the uterus and hypothalamus of 50--81-day-old female rats undergoing a 4-day oestrous cycle. In the uterus, the content of nuclear receptor fluctuated in concert with known cyclic changes in the secretion of oestrogen, being maximal at pro-oestrus. Over the period of 50--81 days, the nuclear content at all phases increased with age, again corresponding to known age-related increases in ovarian secretion of oestrogen. This age-related increase in nuclear content, averaged from the values of the different phases in each age group, was related to equivalent increases in uterine wet weight, an increase of 1 pmol of receptor being accompanied by an increase of 80--90 mg. The concentration of cytosol receptor was maintained constant, with respect to wet weight, throughout the cycle and with age, irrespective of changes in nuclear content. In the uterus of normal mature females, translocation of receptor into the nucleus did not lead to depletion of cytosol receptor, suggesting a process of continuous replenishment/synthesis. In the hypothalamus, the nuclear content of oestrogen receptor was also maximal at pro-oestrus. In contrast with the uterus, the content of hypothalamic cytosol receptor was minimal at this phase and reflects depletion of the cytosol receptor, possibly as a result of translocation. The extent of translocation was low compared with that in the uterus and did not alter with age during the age-period studied. This low nuclear binding of the receptor in vivo is discussed in relation to the presence of a cytosol factor, present in limiting amounts, which in vitro mediates the binding of cytosol receptor to oligo(dT)-cellulose. The difference in the physiological response of the uterus and of the hypothalamus to oestrogens may be related to the extent of nuclear binding of receptor.     

Effects of infantile/prepubertal chronic estrogen treatment and chemical sympathectomy with guanethidine on developing cholinergic nerves of the rat uterus.

The innervation of the uterus is remarkable in that it exhibits physiological changes in response to altered levels in the circulating levels of sex hormones. Previous studies by our group showed that chronic administration of estrogen to rats during the infantile/prepubertal period provoked, at 28 days of age, an almost complete loss of norepinephrine-labeled sympathetic nerves, similar to that observed in late pregnancy. It is not known, however, whether early exposure to estrogen affects uterine cholinergic nerves. Similarly, it is not known to what extent development and estrogen-induced responses in the uterine cholinergic innervation are affected by the absence of sympathetic nerves. To address this question, in this study we analyzed the effects of infantile/prepubertal chronic estrogen treatment, chronic chemical sympathectomy with guanethidine, and combined sympathectomy and chronic estrogen treatment on developing cholinergic nerves of the rat uterus. Cholinergic nerves were visualized using a combination of acetylcholinesterase histochemistry and the immunohistochemical demonstration of the vesicular acetylcholine transporter (VAChT). After chronic estrogen treatment, a well-developed plexus of cholinergic nerves was observed in the uterus. Quantitative studies showed that chronic exposure to estrogen induced contrasting responses in uterine cholinergic nerves, increasing the density of large and medium-sized nerve bundles and reducing the intercept density of fine fibers providing myometrial and perivascular innervation. Estrogen-induced changes in the uterine cholinergic innervation did not appear to result from the absence/impairment of sympathetic nerves, because sympathectomy did not mimic the effects produced by estrogen. Estrogen-induced responses in parasympathetic nerves are discussed, considering the direct effects of estrogen on neurons and on changes in neuron-target interactions.     

Prenatal Exposure to Arsenic and Its Effects on Fetal Development in the General Population of Dalian

To evaluate prenatal exposure to arsenic in the general population and its effects on birth size, we conducted a cross-sectional study in Dalian, China. Arsenic concentration in maternal and cord blood was detected by inductively coupled plasma-mass spectrometry and its effects on birth size were analyzed by multivariate analysis and multiple linear regression analysis. Arsenic concentrations in cord blood were significantly lower than those in maternal blood. A significant positive correlation was shown between maternal and cord blood arsenic concentrations. Maternal arsenic concentration was negatively associated with birth weight, height and chest circumference, and fetal arsenic concentration was negatively associated with head circumference. Our results indicate that arsenic exposure at environmental levels in uterus may pose adverse effects on fetal development.     

Monosodium glutamate impairs the contraction of uterine visceral smooth muscle ex vivo of rat through augmentation of acetylcholine and nitric oxide signaling pathways

The aim of the study was to examine the toxic effects of Monosodium glutamate (MSG), an extensively used food additive, on the contraction of uterine visceral smooth muscle (UVSM) in rat and to elucidate the probable neurocrine mechanism involved in it. MSG produced significant potentiation of the force and inhibition of frequency of uterus recorded ex vivo in chronic MSG exposure and in single dose acute experiments. MSG also produced significant potentiation of force of acetylcholine induced contraction and no alterations in atropine induced contraction of uterus. Further, MSG produced significant increase in force and frequency of contraction of neostigmine incubated uterus. We have found significant potentiation of the post pause force of contraction of uterus when MSG was applied in adrenaline incubated uterus. MSG also produced significant decrease in frequency of contraction of sodium nitroprusside incubated uterus; increase in frequency of N-ω-Nitro-l-Arginine Methyl Ester incubated uterus and no significant changes in frequency of contraction of methylene blue incubated uterus. These results indicate that MSG potentiates the force of contraction of UVSM predominantly by augmenting the activity of cholinergic intrinsic efferents and inhibits the frequency of contraction probably by augmenting the activity of nitrergic efferents. In conclusion, MSG potentiates the force and inhibits the frequency of contraction of UVSM, and the MSG induced effect is probably mediated through the augmentation of acetylcholine and nitric oxide signaling pathways.     

Impaired glucose homeostasis during postimplantation pregnancy in the mouse following acute exposure to ethanol, with particular reference to the uterus and embryo.

Dramatic changes in the levels of plasma glucose and lactate and liver glycogen were observed in mice, given an intraperitoneal injection of ethanol (3.5 g/kg body weight) on Day 9 of pregnancy, during the period of time (6 h) required to clear the drug from the circulatory system. These alterations were accompanied by significant changes in the rates of accumulation of some glycolytic and citric acid cycle intermediates in the uterus, including glucose-6-phosphate, fructose-6-phosphate, lactate, citrate, alpha-ketoglutarate, and succinate. Although the changes in some metabolic parameters were very transient, not all metabolites returned to control values by the time that the drug had been cleared from the maternal system. Alcohol also impaired the capacity of Day 9 mouse embryos to metabolize [14C]glucose under culture conditions in vitro and significantly increased the amount of the aldohexose accumulating in the fetal membrane fluid when administered on Day 14 of pregnancy. However, ethanol neither influenced the ratio of NADH to NAD+ in the uterus nor changed the glycolytic and respiratory activity of the uterine endometrium when coincubated with the tissue in vitro. The results indicate that glucose homeostasis is impaired in both the embryo and the maternal system of mice acutely exposed to alcohol during the teratogenically sensitive period of postimplantation pregnancy and support the thesis that this phenomenon may present an important mechanism underlying the embryo-toxic effects of alcohol consumed under "binge" drinking conditions during pregnancy. However, the results also suggest that the effects registered at the uterine level most likely involve stress reactions and acetate rather than primary actions of the drug on the organ.     

Insulin signaling in the liver and uterus of ovariectomized rats treated with estradiol

We used rat hepatic and uterine tissues to examine the impact of estradiol (E2) on insulin (INS) signaling. Ovariectomized (OVX) female Wistar rats were treated with E2 (20 microg/kg b.wt., i.p.) and used for the experiment 6h after E2 administration. To highlight E2 effects on tyrosine phosphorylation of INS receptor (IR) and INS receptor substrates (IRSs) and IRSs association with p85 subunit of phosphatidylinositol 3-kinase (PI3-K) in the context of INS signaling, E2-treated OVX rats were also injected with INS (20 IU, i.p.), 30 min before the experiment. Treatment with E2 did not change the levels of plasma INS and glucose (Glu). However, it significantly decreased the free fatty acid (FFA) level and increased uterine weight. Furthermore, the results show that E2 had no effect on the content of hepatic IR protein, but significantly increased IR protein content in the uterus and decreased IR tyrosine phosphorylation in both the liver and uterus. Compared to the control, hepatic IRS-1 and IRS-2 were significantly decreased and increased, respectively, after E2 treatment. Protein content of both molecules, IRS-1 and IRS-2, was increased in uterine tissue after E2 administration. Protein content of the p85 subunit of PI3-K and that of protein kinase B (Akt) were increased in the uterus, with no changes in the liver. The results suggest that E2 treatment induces tissue-specific changes in INS signaling. The consequences of E2 treatment on INS signaling molecules are more apparent in the uterus, but their physiological relevance for INS action is probably greater in the liver.     

Effects of a phytoestrogen diet on estrogen-dependent reproductive processes in immature female rats.

The study reported here examined the effects of a phytoestrogen diet on progestin receptor induction, vaginal opening, and the onset and maintenance of vaginal cycles in developing female rats. A natural dietary concentration (0.01%) of the isoflavonoid coumestrol was incorporated into the AIN semipurified diet and fed from 21 to 24 days (acute treatment) or from 22 to 60 days (chronic treatment). Progestin receptor induction was observed in the uterus, pituitary, and hypothalamus-preoptic area following acute treatment. Responses were more marked in the uterus and pituitary than in the hypothalamus-preoptic area. Vaginal opening was accelerated by 4 days during chronic coumestrol treatment and occurred at a lighter body weight. Vaginal cycles began on vaginal opening and did not differ in regularity from those of control animals. However, irregular cycles were observed in coumestrol-treated animals at 116 to 131 days, suggesting that chronic coumestrol treatment may have induced some permanent changes in reproductive function. These findings demonstrate that plant estrogens, at natural dietary levels, produce significant, agonistic actions in several estrogen-dependent tissues and processes.