Progesterone dependent uptake of uteroglobin by rabbit endometrium

Unlabeled or 3H-labeled UGL, isolated from rabbit lungs, was injected intraluminally into the uteri of ovariectomized low dose progesterone substituted and unsubstituted animals as well as into mated animals on the fifth day of pregnancy. It was offered to the endometrium, in this last case, in competition with endogenously synthesized UGL. 3H-labeled IgG served as a control. The animals were killed 24 h after the experiment. Immunohistograms and autoradiograms showed that UGL was taken up by the whole endometrium of the ovariectomized animals but only when progesterone was present. In the preimplantation uterus, uptake was limited to clusters of smaller cells accumulated in the lumen adjacent to the epithelium, whereas IgG remained within the uterine lumen, forming a dense layer on the endometrial surface.     

Uteroglobin and the accumulation of progesterone in the uterine lumen of the rabbit

Summary This study was undertaken to determine whether the influx of progesterone into the uterine lumen of the rabbit, in the preimplantation period, is dependent onuteroglobin (UGL). Rabbits were ovariectomized and, three months later, treated with two defferent doses of progesterone. Purified UGL was injected into one uterine horn and, as a control,immunoglobulin G (IgG) was injected into the other. After four days, the animals were sacrificed their uteri flushed, and the progesterone content of the washes was determined by radioimmunoassay.Animals with the lower serum progesterone level (2.8 ng/ml) had a significantly different uterine horn progesterone content. The hormone accumulation in the horn containing UGL was 2.3 to 7.5 times higher than in the horn containing IgG. Animals with a higher serum progesterone level (7.2 ng/ml) showed no differences. The hormone content was equally high in both horns, presumably due to the synthesis of endogenous UGL being reactivated by the hormone treatment.The validity of these experiments as models for the events during early pregnancy and the physiological role of progesterone available inside the uterus are discussed.     

Detection of a progesterone-dependent secretory protein synthesized by cat endometrium

Uterine flushings and culture media from endometrial explants incubated in the presence of radiolabeled amino acids were analyzed using one-(1-D) and two-dimensional (2-D) gel electrophoresis to identify proteins synthesized by the endometrium and subsequently released into the uterine lumen. 1-D and 2-D analyses of uterine flushings and culture media of endometrial explants obtained from 7- to 11-day pregnant cats (pre-implantation) showed a Mr 30,000 protein that appeared on 2-D gels as a family of macromolecules with isoelectric points between 6.5 and 7.0. This family of macromolecules was also present in the culture media of implantation-site tissue obtained from 12- to 16-day pregnant cats and of nonimplantation-site endometrium obtained form 12- to 28-day pregnant cats. The Mr 30,000 protein was absent in uterine flushings and culture media from estrous and 3- to 5-day-pregnant cats. In ovariectomized, steroid-treated animals, the Mr 30,000 protein was only detected in flushings and media from those animals treated with progesterone, regardless of the presence or absence of estradiol-priming and/or simultaneous estradiol treatment. In daily flushings obtained from ovariectomized, steroid-treated cats equipped with an indwelling uterine catheter, the Mr 30,000 protein was absent during the 14 days of estradiol treatment and was first detected 3-4 days after the onset of estradiol plus progesterone treatment. This protein was not detected in serum from estrous, 9-day pregnant, ovariectomized, and ovariectomized, steroid-treated animals. This study shows that 1) a progesterone-dependent protein, with an approximate molecular weight of 30,000 and an isoelectric point of 6.5-7.0, first appears within the uterine lumen soon after the arrival of the blastocyst and continues to be present during implantation; 2) the synthesis and release of the Mr 30,000 protein is dependent on progesterone regardless of the presence or absence of estradiol; and 3) the onset of secretion of the Mr 30,000 protein requires 3-4 days of continuous progesterone treatment in the estradiol-primed cat.     

Uteroglobin in the rabbit

Summary Rabbit uterine uteroglobin (UGL) was studied by electrophoretic and immunological methods following normal copulation, after ovariectomy and progesterone treatment, 17-oestradiol and combined progesterone treatment, 17-oestradiol treatment alone and after HCG-induced pseudopregnancy. Electrophoretic studies show the amount of ULG in uterine secretions, the immunological investigations indicate the intracellular localization of ULG and the distribution of ULG-positive cells in the endometrium.No obvious differences were found between the uteri 7 days after injection with chorion-gonadotropin and those 7 days following normal copulation. No differences could be demonstrated between the uteri of animals 35 days following ovariectomy and subsequent progesterone treatment on Days 31–33 and those of normal 7 d. post coitum (p.c.) animals. Uteri from animals treated with progesterone on Days 2–5 p.c. contained more ULG-positive cells than controls. 17-oestradiol treatment with and without subsequent progesterone treatment resulted, in both gravid and ovariectomized animals, in the formation of a tall columnar endometrial epithelium. Treatment with 17-oestradiol on Days 1 and 2 p.c. led to a decrease in the number of UGL-positive cells at 7 days p.c. Even after ovariectomy with 17-oestradiol substitution, UGL-positive cells were still present in the endometrium. However a secretion of any magnitude could not be detected. The importance of differentiation between synthesis and secretion (= release) as distinct phases of the glandular response is especially emphasised by the latter findings.Supported by Grant No. Ki 154/5-6, Deutsche Forschungsgemeinschaft     

Estrogen- and progesterone-dependent secretory changes in the uterus of the sheep.

This study was undertaken to determine the effects of 17 beta-estradiol (E) and progesterone (P) on polypeptide synthesis and release from the uterus of the sheep. Uterine flushings (UF) and endometrium were obtained from ovariectomized untreated animals, ovariectomized animals treated with E (approximately 5-10 pg/ml) for 6 days (6E) and ovariectomized animals primed with E for 6 days then treated with P (approximately 1.5-3 ng/ml), in the continued presence of E, for an additional 6 days (6EP). Endometrium was cultured (24 h) in the presence of 3H-leucine (3H-leu) or 3H-glucosamine (3H-glcN), and newly synthesized and released proteins were detected in culture media by fluorography of 10% SDS gels. The quantity of proteins in UF and radiolabeled proteins in explant culture media did not change between treatment groups (p < 0.05). Qualitative changes in the synthesis and release of proteins were observed depending on the steroid treatment. An M(r) 57,000 protein was present in UF and 3H-leu-labeled culture media obtained from animals treated only with E and an M(r) > 200,000 was present in 3H-leu-labeled culture media of endometrium obtained from 6E and 6EP animals. An M(r) 44,000 protein was present only in UF from 6EP animals but could not be detected in endometrial culture media from animals undergoing this steroid treatment. These data show that the endometrium of the ovariectomized sheep undergoes alterations in secretory protein patterns which depend on the presence of E and P.     

Ultrastructural studies of the effect of steroid hormones on pars recta secretions in Bufo arenarum

In amphibians, eggs are released from the ovaries into the coelomic cavity after hormonal stimulation, while related preparatory events occur in the oviducts. We have reported an association between the biological activity of the pars recta (PR), the female reproductive cycle, and ultrastructural modifications of PR epithelium induced by steroid hormones in Bufo arenarum. This article describes (1) the electron microscopic features of PR epithelium and its secretions after ovariectomy; and (2) the effect of either 17β-estradiol, 5α-dihydrotestosterone, progesterone, or a combination of progesterone plus 17β-estradiol on PR epithelium and secretions in ovariectomized animals. Our results indicate that treatment solely with 5α-dihydrotestosterone, 17β-estradiol or progesterone is ineffective in counteracting the effect of ovariectomy, although some effect was noted. The PR secretions of ovariectomized control and ovariectomized animals stimulated with any one of the steroid hormones analyzed, are composed of flocculent material and membranous vesicles. By contrast, treatment of ovariectomized animals with a combination of 17β-estradiol and progesterone, restores the appearance of the pars recta epithelium to that of the nonovariectomized control animals. Progesterone, in the presence of 17β-estradiol, appears to be responsible for triggering the release of secretory granules into the PR lumen. J. Morphol. 231:1–10, 1997. © 1997 Wiley-Liss, Inc.     

Hormonal regulation of apoptosis in the endometrium of common marmosets (Callithrix jacchus)

Phase-dependent apoptotic changes in the human endometrium during an ovarian cycle imply a potential role of steroids in the regulation of apoptosis. The present study was undertaken to determine the direct role of hormones in endometrial apoptosis in marmosets (Callithrix jacchus), a primate species which shows similarity to humans in terms of the cycle length and pattern. Endometrial apoptosis was detected by 3'-end labeling (TUNEL) in various phases of ovarian cycle in naturally cycling healthy marmosets (n=14) and also in ovariectomized marmosets (n=13) treated with either estradiol alone (E) or progesterone alone (P) or estradiol followed by progesterone (E+P). Expressions of apoptosis associated genes such as Bcl-2 family members (Bax and Bcl-2), proliferating cell nuclear antigen (PCNA)--a proliferation marker and steroid receptors, ERalpha and PR A were analysed by immunohistochemical methods. Apoptosis was intense in the glandular epithelial cells of endometrium during the mid-luteal phase as compared to other phases in naturally cycling animals; in the E+P group as compared to other groups of ovariectomized animals (P<0.05). Pronounced apoptosis in the mid-luteal phase was accompanied by the increased expression of Bax in glandular epithelial cells; while Bcl-2 immunoreactivity remained unchanged. PCNA expression was higher in the naturally cycling animals in the follicular phase and in the E group of the ovariectomized animals as compared those in the other groups. Immunoreactive ERalpha and PR A in glandular epithelial cells were most abundant during early follicular phase in naturally cycling animals and in both E and E+P groups among the ovariectomized animals. The present study highlights the importance of apoptosis in endometrial remodeling during the ovarian cycle and secondly, the role of both estradiol and progesterone in the regulation of apoptosis.     

Effect of ovine trophoblast protein-1, oestrogen and progesterone on oxytocin-induced phosphatidylinositol turnover in endometrium of sheep

In Exp. 1, endometrium was collected from Day-15 cyclic ewes and effects of oTP-1, oxytocin and oTP-1 + oxytocin, in various temporal relationships, on phosphatidylinositol (PI) turnover were determined. Co-treatment of endometrium with oTP-1 and oxytocin inhibited stimulatory effects of oxytocin, while treatment with oTP-1 before and during oxytocin administration had no effect. Turnover of PI was unaffected by oTP-1 alone. In Exp. 2, ovariectomized ewes were treated with progesterone (50 mg/day) for 10 days and then oestrogen (100 micrograms/day) for 2 days and endometrium was collected. Oxytocin stimulated PI turnover in endometrium, but oTP-1 had no effect alone or in combination with oxytocin. In Exp. 3, ovariectomized ewes were treated with corn oil (1 ml/day), oestrogen (50 micrograms/day), progesterone (50 mg/day) or progesterone + oestrogen for 10 days and endometrium was collected. Oxytocin stimulated PI turnover only in ewes that received progesterone. oTP-1 alone had no effect on PI turnover, while co-treatment of endometrium with oxytocin and oTP-1 stimulated PI turnover in ewes treated with progesterone, but not progesterone and oestrogen. Pretreatment of endometrium with oTP-1 stimulated PI turnover when ewes were treated with progesterone or progesterone + oestrogen. Pretreatment of endometrium with oxytocin and then treatment with oTP-1 inhibited PI turnover compared to treatment with oxytocin alone. In Exp. 4, ovariectomized ewes were treated as in Exp. 2. Catheters were placed into the uterine horns and ewes received oTP-1 into one horn and serum into the other twice daily on Days 10-12 of steroid treatment. Endometrium collected on Day 13 was used to measure PI turnover and received either no treatment or oxytocin. Oxytocin stimulated PI turnover in endometrium of these ewes and in-vivo treatment of the ewes with oTP-1 had no effect on PI turnover. These results indicate that antiluteolytic effects of oTP-1 are not mediated by inhibiting effects of oxytocin on phosphatidylinositol turnover if oxytocin receptors are present and that uterine responsiveness to oxytocin is progesterone dependent.     

Relative Binding Affinity of Antiprogestins Zk 98.299 And Zk 98.734 For Progesterone Receptors in the Endometrium and Myometrium of Bonnet Monkeys

Abstract

Progesterone bound with high affinity to the endometrial and myometrial cytosol of ovariectomized bonnet monkeys pretreated with estradiol benzoate and progesterone. The equilibrium dissociation constant (K_d) of ³H-progesterone was 4.5 nM and 5.5 nM and the binding capacity was 1.7 nM and 1.4 nM for the endometrial and myometrial receptors, respectively. This experimental ‘model’ was used to assess the relative binding affinity (RBA) of progesterone, ZK 98.299 and ZK 98.734. The tested compounds showed competitive binding to cytoplasmic progesterone receptors. The RBF of progesterone in the endometrium (100) was more than that of ZK 98.299 (25.1) and ZK 98.734 (17.8). A similar RBA pattern was observed in the myometrial cytosol. Both ZK 98.299 and ZK 98.734, like progesterone, displaced the ³H-progesterone bound to the receptors. The administration of ZK 98.299 or ZK 98.734, during the mid-luteal phase, has been reported to shorten the cycle length in bonnet monkeys and marmosets, respectively. These compounds, therefore, appear to intercept the progesterone action by blocking progesterone binding sites in the target tissue. Since ZK 98.299 has higher binding affinity than ZK 98.734, it may be a more potent progesterone antagonist.     

Uptake and accumulation of tritiated uteroglobin by day-6 rabbit blastocysts

Summary Uptake of uteroglobin (UGL) by day-6 rabbit blastocysts and the intracellular fate of this protein were studied by light- and electron-microscopic autoradiography, immunocytochemistry and acid-phosphatase cytochemistry. UGL, labelled with N-succinimidyl-(2-3-³H)-propionate, was administered to embryos in vitro for 15 min to 4 h. The kinetics, determined from light-microscopic autoradiographs, showed a continuous uptake of the labeled protein over a 4-h period of incubation. At the ultrastructural level, increasing numbers of silver grains and an intense UGL immunoreaction in protein vacuoles and crystalloid bodies of trophoblast cells indicated that ³H-UGL had accumulated in these organelles. The presence of crystalloid inclusions in protein vacuoles suggests their origin by a condensation of the protein content, including UGL. Lysosomes containing radioactivity were rarely found, suggesting a very low degradation rate of the ³H-UGL. Protein vacuoles and crystalloid bodies exhibited no acid phosphatase reaction. The enzyme was mainly found outside the basal and lateral cell membranes of trophoblast cells, and on the rough endoplasmic reticulum of endoderm cells.     

Oviduct response to prostaglandins: Influence of estradiol and progesterone

Oviductal motility was measured in the isthmus of ovariectomized New Zealand rabbits. The effects of estradiol and progesterone on spontaneous motility and on the response of the oviduct to exogenously administered prostaglandin E₁ (PGE₁) and PGF_2α were determined. Estradiol treatment significantly increased both the amplitude (P<0.05) and frequency (P<0.01) of spontaneous contractions. The amplitude of spontaneous activity was less following progesterone treatment than following estradiol treatment (P<0.05). Progesterone treatment increased the duration of oviduct response to PGE₁ (P<0.05). Estradiol treatment had no effect on the response to PGE₁. Increased oviductal activity caused by PGF_2α lasted significantly (P<0.01) longer in ovariectomized, untreated animals than in ovariectomized animals treated with estradiol or progesterone. Progesterone was more effective than estradiol in decreasing the duration of the response to PGF_2α. These effects of steroid hormones on the responsiveness of the oviduct to PGE₁ and PGF_2α could contribute to the physiological control of egg transport. The nadir of ovarian hormone influence, as in the recently ovariectomized animals and as occurs immediately after ovulation, is associated with a high responsiveness of the oviduct to PGF_2α. This could effectively increase isthmic occlusion and prevent the eggs from passing through the oviduct prematurely. The gradual increase in ovarian estradiol and progesterone secretion during the 3 days following coitus could result in decreased responsiveness to PGF_2α and increased responsiveness to PGE₁. These changes might cause relaxation of isthmic tone and allow movement of eggs through the isthmus into the uterus.     

Varying effects of an IUD on decidualization in mice.

Chronically implanted IUDs consisting of silk suture threads induced decidualization in regions of the uterus remote from the suture site in ovariectomized mice treated with a regimen of progesterone and oestrogen which sensitizes the uterus to a decidual stimulus. In these conditions the IUDs did not inhibit decidualization induced by instilled oil, although they did so in pregnant animals of the same strain. Varying the dose of progesterone and oestrogen did not produce conditions in which IUD's inhibited oil-induced decidualization in ovariectomized mice and progesterone treatment did not prevent IUDs inhibiting decidualization in pregnant animals. However, when ovariectomized mice, sensitized as before, were primed repeatedly with oestrogen to simulate continuing oestrous cycles after IUD insertion, the IUD's inhibited oil-induced decidualization. This involved the premature loss of instilled oil from the uterine lumen and was associated with heavy infiltration of leucocytes into the luminal epithelium. Numbers of leucocytes free in the uterine lumen did not appear to be critical. It appears that contact between the oil and the luminal epithelial surface must be sustained for some length of time to induce a decidual reaction; brief contact is not sufficient to trigger the response.     

Modulation of the action of chorionic gonadotropin in the baboon (Papio anubis) uterus by a progesterone receptor antagonist (ZK 137. 316)

Signals from the developing mammalian blastocyst rescue the corpus luteum (CL) and modulate the uterine environment in preparation for implantation and early pregnancy. Our previous studies demonstrated that both short- and long-term administration of chorionic gonadotropin (CG) markedly alters the morphology and the biochemical activity of the receptive endometrium. Because the effects of CG were superimposed on a progesterone-primed endometrium, this study was undertaken to determine if the inhibition of progesterone action by progesterone receptor antagonists (PRa) in intact and ovariectomized baboons would alter the action of CG on the endometrium at the time of uterine receptivity. In the short-term hCG-treated baboons, the PRa reduced the epithelial plaque reaction, completely inhibited alpha-smooth muscle actin (alphaSMA) expression in stromal fibroblasts, and induced the reappearance of the progesterone (PR) and estrogen (ERalpha) receptors in epithelial cells. However, this treatment protocol had no effect on the expression of glycodelin in the glandular epithelium. In contrast, glycodelin expression in addition to alphaSMA was suppressed in the ovariectomized animals. In the long-term hCG-treated baboons, the PRa had a similar effect on both alphaSMA, PR, and ER. In addition, this treatment also resulted in an inhibition of glycodelin expression in the glandular epithelium. These results indicate that blocking the action of progesterone on the endometrium even for a short period of time has a profound effect on the hCG-induced response in stromal fibroblasts. In contrast, for the diminution of glandular epithelial function in the presence of an ovary requires prolonged inhibition of progesterone action, suggesting a potential paracrine effect on the endometrium from the CL in response to hCG.     

Habitat Capacity for Cougar Recolonization in the Upper Great Lakes Region

Background

Recent findings indicate that cougars (Puma concolor) are expanding their range into the midwestern United States. Confirmed reports of cougar in Michigan, Minnesota, and Wisconsin have increased dramatically in frequency during the last five years, leading to speculation that cougars may re-establish in the Upper Great Lakes (UGL) region, USA. Recent work showed favorable cougar habitat in northeastern Minnesota, suggesting that the northern forested regions of Michigan and Wisconsin may have similar potential. Recolonization of cougars in the UGL states would have important ecological, social, and political impacts that will require effective management.

Methodology/Principal Findings

Using Geographic Information Systems (GIS), we extended a cougar habitat model to Michigan and Wisconsin and incorporated primary prey densities to estimate the capacity of the region to support cougars. Results suggest that approximately 39% (>58,000 km²) of the study area could support cougars, and that there is potential for a population of approximately 500 or more animals. An exploratory validation of this habitat model revealed strong association with 58 verified cougar locations occurring in the study area between 2008 and 2013.

Conclusions/Significance

Spatially explicit information derived from this study could potentially lead to estimation of a viable population, delineation of possible cougar-human conflict areas, and the targeting of site locations for current monitoring. Understanding predator-prey interactions, interspecific competition, and human-wildlife relationships is becoming increasingly critical as top carnivores continue to recolonize the UGL region.     

Oxytocin-stimulated production of prostaglandin F2α by isolated endometrium of rabbit: Modulation by ovarian steroids

To test the hypothesis that ovarian steroid hormones modulate oxytocin-induced release of prostaglandin F_2α (PGF_2α) from uterine endometrium, 2 ovariectomized rabbits were pretreated with progesterone (5 mg/day for 10 days), 2 with estradiol-17β (25 μg/day for 10 days), 2 with both steroids, and one with sesame oil only. On the last day of treatment, endometrial fragments were excised and incubated in vitro with or without oxytocin (100 μU/ml). Although endometrium from rabbits pretreated with combined steroids released more PGF_2α immediately after excision than did tissue from animals pretreated with either steroid by itself, endometrium from animals pretreated with estrabdiol-17β alone released the most PGF_2α during sustained incubation in vitro. Moreover, only this tissue exhibited significant oxytocin-dependent release of PGF_2α. At the dosages used, progesterone completely antagonized both of these effects of estradiol-17β. The results support the hypothesis that ovarian steroid hormones regulate oxytocindependent release of PGF_2α from endometrial cells. A possible mechanism of action is suggested.     

Characterization of estrogen and progesterone receptors in monkey endometrium: methodology and effects of estradiol and/or progesterone on endometrium of castrate monkeys.

Appropriate methods for repeated surgical collection of endometrial tissue from rhesus monkeys, and characterization of cytosol and nuclear estrogen (E₂) and progesterone (P) receptors (R) are described. Tissue collection was made in the mid-luteal phase at abdominal fundal hysterotomy. Functional status of the ovaries was determined by visual inspection and RIA of E₂ and P in serum. Receptor assay procedures were devised permitting the measurement of total cytosol and nuclear receptor concentration. Sucrose density gradients of labelled cytosol were made and a 4S saturable binding component for ³H P and for ³H E₂ were found. Equilibrium dissociation constants of ³H E₂ and ³H R5020 were 2.1×10^?10M and 3.6 × 10^?9M, respectively. These binding characteristics are similar to those found in human endometrium and suggest that these surrogate primates have extensive utility in investigation of factors influencing E₂R and PR concentrations in endometrial tissue during the menstrual cycle and implantation. Simulated menstrual cycle were produced in 20 castrate monkeys by sequential treatment with estradiol and progesterone in silastic capsules. RIA of E₂ and P, and gonadotropins in peripheral serum provided assuredness of the hormonal status of each monkey under treatment. Cytosol and nuclear receptors for E₂ and P were measured in the endometrium after different intervals of the treatment. E₂ receptor (E₂R) levels were not changed during the estrogen sequence, but were lowered by progesterone therapy in both cytosol and nuclear components. Progesterone receptor (PR) synthesis in cytosol was induced by exogenous estrogen. The total concentration of PR decreased with the uptake of P by the cell; meanwhile, the ratio of cytosol to nuclear P receptors declined. These data suggest that this sequential estrogen-progesterone regimen induces the changes in E₂R and PR patterns in the endometrium of ovariectomized monkeys which occurs due to ovarian cyclicity in the normal menstrual cycle.     

Synthesis of steroids in postimplantation mouse embryos cultured in vitro

Steroid and total lipid synthesis have been assessed in postimplantation stage mouse embryos cultured in vitro from the blastocyst to early somite stage. A large increase in acetate incorporation into these compounds is observed during this period. Cholesterol (60–70%), lanosterol (1–15%), and a fraction containing pregnenolone (0–5%) are the major components of the embryo-associated steroid fraction. When embryos are labeled with [³H]pregnenolone, ³H-labeled progesterone, pregnanedione, and a compound identified as acylpregnenolone are produced and secreted into the medium. Production of progesterone and pregnanedione, but not acylpregnenolone, is severely inhibited by the drug cyanoketone (1 μM). Another drug, SU-10603 (10 μM), severely inhibits pregnanedione production, with only a partial repression of progesterone synthesis, and no effect on acylpregnenolone synthesis. Neither drug affects embryonic development. When embryonic tissues were carefully separated and analyzed for their ability to metabolize [³H]pregnenolone it was observed that all tissues (embryo/yolk sac, yolk sac, and trophoblast) can produce progesterone and acylpregnenolone from pregnenolone. Only embryo/yolk sac and yolk sac, but not trophoblast tissue, can produce pregnanedione. The significance of these observations in relation to metabolic communication between the embryo and its mother is discussed.     

Ovarian steroid-regulated synthesis and secretion of complement C3 and factor B in mouse endometrium during the natural estrous cycle and pregnancy period.

We demonstrate the presence of complement factor B (Bf) and complement C3 in uterine luminal fluid collected from estrogen-stimulated immature and adult female mice. We examined the synthesis and secretion of these two proteins in mouse endometrium at various stages of the natural estrous cycle and during the pregnancy period. The mRNA levels of these two proteins increased markedly in proestrus and estrus and declined sharply in metestrus to an undetectable level. The Bf mRNA remained undetectable, whereas a readily detectable C3 mRNA level reappeared, in diestrus. Meanwhile, these two proteins were immunolocalized to the apical cytoplasm of glandular and luminal epithelial cells of the endometrium during the estrous cycle. Administration of an estrogenic steroid to immature or ovariectomized adult mice markedly stimulated the expression of Bf, C3, and their RNA messages in the endometrium, whereas injection of progesterone alone to ovariectomized animals did not stimulate their expression. Expression of C3 was remarkably enhanced, whereas that of Bf changed only slightly, after injection of combined estrogen and progesterone to ovariectomized animals. In pregnant mice (Day [D] 1 = day of vaginal plug), Bf mRNA was at a high level on D1 and D2, dropped to an almost undetectable level from D3 to D8, and then increased to a low level thereafter until delivery. The C3 mRNA was at a high level on D1, dropped on D2 to an almost undetectable level from D3 to D9, increased to a very high level from D10 to D18, and then declined sharply before delivery. Immunohistochemical patterns of both proteins in the endometrium during preimplantation were positively correlated with changes in their mRNA levels.     

Uptake and release of H prostaglandins E2 and F2α in uterin strips isolated from ovariectomized rats. Influence of progesterone

The accumulation and output of ³H -prostaglandins (PGs), E₂ and F₂α, into and from uterine strips isolated from ovariectomized rats, either in presence or in absence of exogenous progesterone, were explored. Tissue-to-medium ratio of ³H - counts (T/M-ratio), was determined. The same was done in solutions containing ¹⁴C-sucrose. During a 60 min incubation period in a solution containing ³H -PGF₂α, a net accumulation of radioactivity was evident in control (no progesterone) uterine slices. The T/M-ratio for ³H-PGF₂α, increased with time, reaching maximal values at 45 min. Progesterone (100 ug.ml⁻¹) attenuated the uptake process, as evidenced by stable values of T/M-ratio, as time progressed. On the other hand, control T/M-ratio for fluenced by the presence of exogenous progesterone. Regarding labelled PG release from the tissue, it was observed that, during an experimental period of 60 min, most tritium from control slices was released within the first 30 min after incubation with ³H -PGF₂α, whereas, following the presence and subsequent removal of exogenous progesterone, the bulk of ³H -released took place at 6–70 min. On the other hand, the release of ³H after an incubation with ³H -PGE₂, was also maximal as that for ³H -PGF₂, α within the first 30 min and resulted not altered after a period of exposure and removal of progesterone. The foregoing results suggest an specific pharmacological effect of progesterone, attenuating the uptake and retarding the outflow of PGF₂α, but not that of PGE₂, into and from uterine slices of ovariectomized rats. Findings reported herein are discussed in terms of progesterone priming and withdrawal, in relation to PGF₂α fluxes in the rat uterus during the sex cycle, as well as in relation to PG binding to tissue receptors.