Paracrine regulation of epithelial progesterone receptor by estradiol in the mouse female reproductive tract

Regulation of progesterone receptor (PR) by estradiol-17beta (E(2)) in mouse uterine and vaginal epithelia was studied. In ovariectomized mice, PR expression was low in both vaginal stroma and epithelium, but high in uterine epithelium. E(2) induced PR in vaginal epithelium and stroma, but down-regulated PR in uterine epithelium. Analysis of estrogen receptor alpha (ERalpha) knockout (ERKO) mice showed that ERalpha is essential for E(2)-induced PR expression in both vaginal epithelium and stroma, and for E(2)-induced down-regulation, but not constitutive expression of PR in uterine epithelium. Regulation of PR by E(2) was studied in vaginal and uterine tissue recombinants made with epithelium and stroma from wild-type and ERKO mice. In the vaginal tissue recombinants, PR was induced by E(2) only in wild-type epithelium and/or stroma. Hence, in vagina, E(2) induces PR directly via ERalpha within the tissue. Conversely, E(2) down-regulated epithelial PR only in uterine tissue recombinants constructed with wild-type stroma. Therefore, down-regulation of uterine epithelial PR by E(2) requires stromal, but not epithelial, ERalpha. In vitro, isolated uterine epithelial cells retained a high PR level with or without E(2), which is consistent with an indirect regulation of uterine epithelial PR in vivo. Thus, E(2) down-regulates PR in uterine epithelium through paracrine mechanisms mediated by stromal ERalpha.     

Effects of estradiol and progesterone on scent-marking behavior of female rats

The effect of estradiol and progesterone on scent-marking behavior of the female rat is reported. Estradiol followed by progesterone injection to ovariectomised rats results in an increase in marking rates. This suggests an endocrine base to the changes in scent-marking behavior that are known to occur with the rat estrous cycle.     

Effects of estradiol and progesterone on the reproductive tract and on uterine sex steroid receptors in female lambs

The effects of estradiol-17 beta (E(2)) and progesterone (P) on the reproductive tract and on uterine estrogen receptors and P receptors were studied in 2-mo-old female lambs (n = 11). On Days 0, 1 and 2, E(2) (1 ug/kg, Group E, n = 4), P (0.3 mg/kg, Group P, n = 4) or corn oil (control) vehicle (Group C, n = 3) were administered, and in Day 3 all lambs were slaughtered. Group E (n = 12) had E(2) serum concentrations (mean +/- SEM) of 43.8 +/- 2.2 pmol L , similar to that of the follicular phase; while P concentrations in Group P (n = 12) were similar (2.8 +/- 0.18 nmol L ) to those of the luteal phase of the ewe estrous cycle. The E(2) treatment increased the reproductive tract weight, while P treatment increased only the uterine weight. Both E(2) and P receptors from upper and middle uterine zones (including the myometrium, endometrium and caruncles) were determined by binding assays with tritiated hormones, dextran-charcoal separation and inverse Scatchard analysis. Both the E(2) and P treatments decreased E(2) and P receptor concentrations in upper and middle zones, although the upper zone had higher receptor concentrations than the middle zone (P < 0.01). E(2) receptor concentrations in the upper zone (mean +/- SEM, fmol mg prot) were 1236 +/- 34, 667 +/- 80 and 444 +/- 103 for Groups C, P and E, respectively. The P receptor concentrations were 2434 +/- 135, 1273 +/- 102 and 1536 +/- 213 for the same groups. The high uterine P receptor concentrations allowed P action without prior estrogen priming of female lambs. The present results suggest that E(2) and P might down-regulate their own and each other's receptors during development. The biological responses induced by E(2) and P, as measured by the reproductive tract weight, demonstrated that at an early stage of development uterine receptors are physiologically active.     

Activation of AMPA receptors inhibits prolactin and estradiol secretion and delays the onset of puberty in female rats

Previous experiments have evidenced the neuroendocrine role of AMPA receptors. Present studies were carried out to obtain information on the role of these receptors in the control of the onset of puberty. To this end, female rats were i.c.v. injected with vehicle or AMPA (agonist of AMPA receptors: 0.1 or 0.5 nmol/day) between 26 and 30 days (Experiment 1), or 30 and 34 days (Experiment 2) of age. Serum concentrations of PRL, LH and estradiol were measured before drug administration, 10 min after the last injection, at vaginal opening (VO) and at first estrus (FE) presentation. In both experiments, AMPA administration inhibited PRL and estradiol secretion without affecting LH release. When AMPA was administered between 26 and 30 days a significant delay in the day of vaginal opening was observed. These results confirmed the inhibitory effect of AMPA on PRL secretion and suggests a role of AMPA receptors in the control of puberty onset.     

Effects of estradiol and progesterone on the sensitivity to pain and on morphine-induced antinociception in female rats

Long-term ovariectomized (OVX) rats were exposed to 2- or 14-day replacement with pellets made of cholesterol (CHOL), estradiol (E2), progesterone (P4), or a combination of E2 and P4. Following the treatment with steroids the antinociceptive effect of morphine (5 mg/kg,sc) was measured by a hot-plate method. Pellets of E2 (0.5 and 5%) caused dose- and time-dependent reductions of morphine-induced antinociception as compared with OVX rats treated with CHOL pellets. Moreover, OVX rats pretreated with E2 pellets had decreased basic sensitivity to nociceptive stimulus (hyperalgesia). Treatment for 2 and 14 days with 75% P4 pellets produced significant reduction of MOR antinociception. The low dose of P4 (10% pellet) did not change the effect of MOR on Day 2 but significantly increased the antinociceptive effect of MOR on Day 14. Replacement of OVX rats with one 0.5% E2 pellet plus one 10% P4 pellet resulted in marked inhibition of the antinociceptive effect of MOR on Day 2 as well as on Day 14. Central injection 30 min before MOR of either LHRH antagonist or the antiserum against LHRH into OVX rats pretreated for 14 days with both steroids had no effect on the degree of the antinociception. The results suggest that the effects which ovarian steroids exert on opioid systems vary according to the dose, the duration of treatment, and the type of steroid administered.     

Preference for an estrous female over a non-estrous female evinced by female rats requires dihydrotestosterone plus estradiol

The effects were studied of long-term treatment with testosterone metabolites (dihydrotestosterone, DHT, and estradiol, E2, in sc Silastic implants) on preference behavior of ovariectomized female rats for an estrous female over a non-estrous female. For measuring this behavior a residential plus-maze was used which harbored two ovariectomized “stimulus” females on the top of peripheral boxes, one of which was made estrus by injection of estradiol benzoate and progesterone. When both steroids (DHT plus E2) were circulating simultaneously they evoked preference for an estrous female, while neither steroid by itself sufficed. In earlier work with adult male rats castrated on the day of birth, E2 was effective in the absence of DHT. This sex difference, therefore, seems to have arisen before birth. Further, administration of DHT alone caused a profound lack of interest in both “stimulus” females, which cannot be fully explained by the reduced locomotor activity which has been found to be induced by DHT in earlier Studies.     

Chronic treatment with estradiol restores depressive-like behaviors in female Wistar rats treated neonatally with clomipramine

Neonatal administration of clomipramine (CMI) induces diverse behavioral and neurochemical alterations in adult male rats that resemble major depression disorder. However, the possible behavioral alterations in adult female rats subjected to neonatal treatment with clomipramine are unknown. Therefore, the aim of this study was to explore the effect of neonatal treatment with CMI on adult female rats in relation to locomotion and behavioral despair during the estrus cycle. Also evaluated was the effect of chronic treatment with E2 on these female CMI rats. We found no effects on spontaneous locomotor activity due to neonatal treatment with CMI, or after 21 days of E2 administration. In the FST, neonatal treatment with CMI increased immobility and decreased active swimming and climbing behaviors. Influence of the ovarian cycle was detected only in relation to climbing behavior, as the rats in the MD phase displayed less climbing activity. Chronic E2 administration decreased immobility but increased only swimming in CMI rats. These results suggest that neonatal treatment with CMI induces despair-like behavior in female rats, but that chronic E2 administration generates antidepressant-like behavior by decreasing immobility and increasing swimming, perhaps through interaction with the serotonergic system.     

Effects of progesterone and estradiol benzoate on glutathione dependent antioxidant enzyme activities in the brain of female rats.

The activities of glutathione dependent antioxidant enzymes were measured in subcellular fractions of whole brain homogenates prepared from ovariectomized (OVX) female rats, untreated or treated 2 h or 24 h prior to sacrifice with a single dose of 2 mg progesterone (P) or 5 micrograms estradiol benzoate (EB). Glutathione peroxidase (GSH-Px) activity was not changed following systemic administration of EB, but P increased GSH-Px in the brain of OVX rats 24 h after the treatment. The activity of glutathione reductase (GR) was suppressed by EB short time, only 2 h following treatment, whereas P increased the enzyme activity 24 h after treatment. On the other hand, the activities of catalase (CAT) and glutathione-S-transferase (GST) were not changed following systemic administration of EB or P. The present work was carried out to study the involvement of ovarian steroids, especially P, in the control of GSH-Px and GR activities, and our results suggest that oxidative stress in the brain of female rats may be modulated by the level of progesterone.     

The effect of progesterone and progesterone + estradiol on the morphology of the pineal gland in immature female pigs

Pineal gland of the immature female pigs treated with progesterone and progesterone and estradiol simultaneously were investigated with light and electron microscopy. Both of the applied hormones influenced the structure of the pineal glands. Inhibitory effect of progesterone on the relative volume of mitochondria, granular vesicles and dense bodies of type one was observed. Administration of progesterone and estradiol simultaneously caused more complicated influence statistically significant increase of pinealocyte nuclei volume and at the same time significant decrease of mitochondria and granular vesicles.     

Impairment of spatial learning by estradiol treatment in female mice is attenuated by estradiol exposure during development

High doses of estradiol (E(2)) can impair spatial learning in the Morris water maze, in ovariectomized mice, but the same dose has no effect on adult castrated males. Here, we test the hypothesis that this sex difference is caused by neonatal actions of E(2). In Experiment 1, C57BL/6J pups were given daily estradiol benzoate (EB) or oil injections from the day of birth until postnatal Day 3. Adults were gonadectomized and received EB (s.c.) or oil 28 h before the first day of training, and 4 h before each of four daily training sessions on the Morris water maze. Females given oil as neonates, and EB prior to training displayed the poorest performance. Females that received EB as neonates and EB prior to training were insensitive to the deleterious effects of adult EB and performed better than males given the same hormone treatments. We conducted a second experiment using aromatase enzyme knockout (ArKO) mice. Adult male and female ArKO and wild-type (WT) littermates were gonadectomized and received either injections of oil or EB prior to and during water maze training (as described above). Hormone treatment failed to affect performance, yet, female but not male ArKO mice showed impaired learning compared to WT littermates. Thus, exposure to estradiol during neonatal development can counteract the deleterious effects of EB on adult spatial learning.     

Effects of testosterone and progesterone on the regression of Mullerian ducts induced by estradiol in the female chick embryo

An administration of testosterone or of progesterone to estradiol-treated female chick embryos increased the rate of those presenting a regression of their Müllerian ducts. This observation favoured the hypothesis according to which the regression induced by estrogens depends on the anti-Müllerian hormone of ovarian origin.     

Donepezil plus estradiol treatment enhances learning and delay-dependent memory performance by young ovariectomized rats with partial loss of septal cholinergic neurons

Effects of estrogen therapy on cognitive performance appear to diminish with age and time following the loss of ovarian function. We hypothesize that this is due to a reduction in basal forebrain cholinergic function and that treatment with a cholinergic enhancer can reverse the effect. This study tested whether combining the cholinesterase inhibitor donepezil with estradiol treatment can enhance/restore estradiol effects on cognitive performance in young ovariectomized rats with selective lesions of septal cholinergic neurons. 192IgG-saporin was injected directly into the medial septum to produce selective cholinergic lesions. Rats were then treated with donepezil (Don, daily injections of 3 mg/kg/day, i.p.) or vehicle, and then with 17β-estradiol (E2, administered by silastic capsule implanted s.c.) or an empty capsule. Rats were trained on a delayed matching-to-position (DMP) T-maze task which previous studies have shown is sensitive to ovariectomy and estrogen replacement. Results show that neither estradiol nor donepezil alone significantly enhanced acquisition of the DMP task in rats with cholinergic lesions. Combination therapy was effective, however, depending on the severity of the lesion. Don + E2 significantly enhanced acquisition of the task in rats with partial lesions (< 50% loss of cholinergic neurons), but not in rats with severe lesions. This effect was due largely to a reduction in perseverative behavior. Don + E2 also improved working memory in rats with partial lesions, as evidenced by significantly better performance than controls during increased intertrial delays. These findings suggest that even partial loss of septal cholinergic neurons can reduce effects of estrogen therapy on cognitive performance, and demonstrate that combining a cholinesterase inhibitor with estrogen therapy can help to restore beneficial effects on performance. We propose that combination therapy may have similar beneficial effects in women, particularly in older women who have not used estrogen therapy for many years and are beginning to show signs of cognitive impairment or early Alzheimer's disease.     

Induction of daily PRL surges in rats by chronic treatment with progesterone

The effect of a high plasma progesterone level on the PRL releasing mechanism was investigated in rats of both sexes. Progesterone levels were maintained by implanting silicone tubes filled with the steroid. In the intact female, 6 progesterone tubes (inner diameter 2 mm; outer diameter 3 mm; length 40 mm) were implanted subcutaneously on the estrous day. With 2- to 5- day latent periods, the daily rise in the plasma PRL level was observed coincident with the time of nocturnal surge in the pseudopregnant rats induced by cervical stimulation. The same treatment applied to ovariectomized rats induced by cervical stimulation. The same treatment applied to ovariectomized rats induced diurnal and nocturnal surges. The peak height was lower in ovariectomized rats than that in intact or normal pseudopregnant rats, and was restored to almost the normal range by concomitant implantation of estradiol with progesterone. This latter protocol, however, did not induce any PRL surge in chronically orchidectomized rats. These results suggest that chronically elevated progesterone levels can induce such PRL surges as are observed in pseudopregnant rats, estradiol enhances the magnitude of the PRL surge, and the progesterone sensitive central mechanism, controlling the PRL surge, does not exist in adult male rats.     

Effects of progesterone and estradiol on the reproductive axis in immature diploid and triploid rainbow trout

In fish species, many studies demonstrated the crucial role of estradiol (E2) in the development of the reproductive axis, but progesterone (P) has been described mainly as a precursor steroid and no clear role by itself has been reported. Moreover, a cooperative effect of P (or another progestin) and E2 in fish has never been reported to our knowledge. In the present work, we investigated the effects of P, alone or in combination with E2, on the reproductive-axis of immature rainbow trout (Oncorhynchus mykiss). Liver vitellogenin and estradiol receptor (rtER) mRNA levels increased after E2 treatment, but were unchanged by P treatments as a reflection of peripheral action of steroids. In contrast, at the pituitary level, LH contents increased after E2 and/or P treatments. Focusing on the brain level, we confirmed a clear up regulation of rtER expression by E2 in sterile triploid females, and we also demonstrated a similar stimulating effect of P alone but no cooperative effect together with E2. In conclusion, our data demonstrate that in immature trout, prior to the beginning of the first reproductive cycle, unlike E2, P is able to stimulate the reproductive brain-pituitary axis without affecting vitellogenin synthesis in the liver.     

Influence of chronic treatment with the growth hormone secretagogue Ipamorelin,in young female rats: somatotroph response in vitro

Growth hormone (GH) is secreted in the anterior pituitary gland by the somatotroph cells. Secretion is regulated by growth hormone releasing hormone (GHRH) and somatostatin. Morever, GH secretagogues (GHS) can exert a considerable effect on GH secretion. In order to determine the effects of chronic treatment with the GHS Ipamorelin on the composition of the somatotroph cell population and on somatotroph GH content, an in vitro analysis was performed of the percentage of somatotroph cells (% of total), the ratio of different GH cell types (strongly/weakly-staining) and individual GH content, in pituitary cell cultures obtained from young female rats receiving Ipamorelin over 21 days (Ipamorelin group) and the effects were compared with those of GHRH (GHRH group) or saline (saline group). The ultrastructure of somatotroph cells did not change, but the volume density of secretion granules was increased (P<0.05) by previous in vivo Ipamorelin or GHRH treatment. In 3-day basal pituitary cell monolayer cultures, the percentage of somatotroph cells showed no modifications between groups, nor was there any change in the ratio of strongly/weakly immunostaining GH cells. In the Ipamorelin group alone, in vitro treatment with Ipamorelin (10(-8) M), or GHRP 6 (10(-8) M), or GHRH (10(-8) M) for 4 hours, increased the percentage of somatotroph cells, without modifying the ratio of strongly/weakly immunostained GH cells. Basal intracellular GH content in somatotroph cells over 4 hours was lower in the Ipamorelin group and the GHRH group than in the saline group. Only in the Ipamorelin group did Ipamorelin (10(-8) M), GHRP 6 (10(-8) M) and GHRH (10(-8) M) prompt increased intracellular GH content. These data suggest that, at least in the young female rat, the GHS Ipamorelin is able to exert a dynamic control effect on the somatotroph population and on GH hormone content.     

Regulation of insulin-like growth factor-I and thioredoxin expression by estradiol in the reproductive tract of the prepubertal female lamb

Estradiol (E(2)) has been shown to be an important uterine growth promoting molecule in the ovariectomized (ovx) rat, which increases the mRNA levels of insulin-like growth factor-I (IGF-I) and the redox enzyme thioredoxin. The aim of this study was to explore the role of E(2) in the regulation of IGF-I and thioredoxin in the reproductive tract of the prepubertal female lamb. Twenty 3-month-old lambs were treated with i.m. injections of E(2) at 24 h intervals. The animals were sacrificed 12 or 24 h after the last injection, and 72 h was the longest treatment period. The mRNA levels of thioredoxin and IGF-I were determined by a solution hybridization technique. There was a 5-fold increase in the cervical IGF-I mRNA level 12 h after the first E(2) injection. The uterine IGF-I mRNA level was doubled after 12 h and this increase was maintained during the rest of the experimental period. The IGF-I mRNA level in the oviducts was more than doubled 12 and 24 h after the E(2) injection, then the level decreased towards the initial level. The thioredoxin mRNA level in the cervix was increased 4-fold after 24 h, whereas no significant effect was seen in the uterus. The thioredoxin mRNA level in the oviduct was more than doubled 12 and 24 h after the first E(2) injection. Thus, estradiol regulates the expression of IGF-I and thioredoxin in the reproductive tract of prepubertal lambs.