Uteroglobin in the rabbit. I. Intracellular localization in the oviduct, uterus, and preimplantation blastocyst

Proteome of equine oviducal fluid: effects of ovulation and pregnancy

The equine oviduct plays a pivotal role in providing the optimal microenvironment for early embryonic development, but little is known about the protein composition of the oviducal fluid in the horse. The aim of the present study was to provide a large-scale identification of proteins in equine oviducal fluid and to determine the effects of ovulation and pregnancy. Four days after ovulation, the oviducts ipsilateral and contralateral to the ovulation side were collected from five pregnant and five non-pregnant mares. Identification and relative quantification of proteins in the oviducal fluid of the four groups was achieved by isobaric tags for relative and absolute quantification (iTRAQ) labelling and HPLC–tandem mass spectrometry. The presence of an embryo in the ipsilateral oviducal fluid of pregnant mares induced upregulation of 11 and downregulation of two proteins compared with the contralateral side, and upregulation of 19 proteins compared with the ipsilateral side of non-pregnant mares. Several of these upregulated proteins are related to early pregnancy in other species. The present study represents the first high-throughput identification of proteins in the oviducal fluid of the mare. The results support the hypothesis that the equine embryo interacts with the oviduct, affecting the maternal secretion pattern of proteins involved in pregnancy-related pathways.

Up-regulation of insulin-like growth factor I and uteroglobin in in vivo-developed parthenogenetic embryos

Parthenote embryos are being considered as an alternative source of embryonic stem cells. However, as there is still a dearth of knowledge of this kind of embryos, a better understanding of their biology is needed for their application. In this work, we studied the differences and similarities between parthenotes and normal embryos at the blastocyst stage in vivo developed. We analysed the expression of factor OCT-4, vascular endothelial growth factor (VEGF), insulin-like growth factor I (IGF-I) and uteroglobin (UG) by real-time PCR. To do so, oocytes were recovered and after activation procedure were transferred by ventral middle laparoscopy to receptive does to undergo completely in vivo development. Does were slaughtered 6 days post-ovulation induction, and parthenote and normal embryos were recovered for mRNA expression analysis. Our results reported that parthenotes and normal embryos showed similar mRNA expression for OCT-4 and VEGF. However, IGF-I and UG showed to be over-expressed in parthenote embryos. Thus, our study highlights that despite the in vivo development of parthenotes, they still seem to have an altered expression and, therefore, to be different to normal embryos. The altered expression pattern of parthenote embryos suggests that these embryos should be studied carefully before future application.

Regional differences in uteroglobin biosynthesis along the rabbit oviduct: immunohistochemical and biochemical studies

The biosynthesis of uteroglobin in three regions of the rabbit oviduct was assessed by means of immunocytochemical studies, radioimmunoassay measurements of the protein, and quantitative determinations of its mRNA. Immunocytochemical observations suggested that the number of immunopositive cells and the intensity of their immunolabelling were similar in the distal (infundibular) and the middle regions. In contrast, the isthmic portion appeared to contain less positive cells and weaker immunolabelling. In agreement with these findings, biochemical studies demonstrated that the tissue contents of uteroglobin and its mRNA were similar in the distal and the middle regions whereas the concentrations of both were about three-to four-fold lower in the isthmic portion. The results are discussed in relation to a possible role for uteroglobin in maintaining appropriate environmental conditions for the gametes and the early embryo.

Localization of uteroglobin mRNA by nonradioactive in situ hybridization in the pregnant rabbit endometrium

The distribution of uteroglobin mRNA has been investigated in the endometrial compartments of the rabbit uterus during early pregnancy (day 0.5 p.c.--day 12 p.c.) using nonradioactive in situ hybridization. Digoxigenin-dUTP labeled oligodesoxy-nucleotide-probes (24mer) and an anti-digoxigenin-antibody conjugated with alkaline phosphatase were developed and used. It could be shown, that uteroglobin mRNA localization is restricted to the endometrial epithelium. There are differences in the extent of uteroglobin mRNA expression within the epithelial cells, which is in accord with our interpretation on the existence of different epithelial cell populations. From day 0.5 p.c. to day 9 p.c. the cells of the basal glands express uteroglobin mRNA continuously, whereas the proliferating surface epithelium shows a remarkable fluctuating pattern of uteroglobin mRNA expression. On day 2 p.c. the whole surface epithelium starts to express the uteroglobin message, and up to day 5 p.c. all these cells show a high level of uteroglobin mRNA expression, which drops significantly on day 6 p.c., when significant changes in the cyto-morphology of the surface epithelium for implantation occur. On day 7 p.c., there is no more uteroglobin mRNA expression in the surface epithelium, however remaining expression in the basal glands. The latter is evident up to day 9 p.c. From day 10 p.c. onwards, neither the luminal nor the deep glandular epithelium express any uteroglobin mRNA. Our observations on the cellular level have been continued in parallel studies on endometrial homogenates by Northern Blot analysis of uteroglobin mRNA (600 bases). Finally, it is discussed whether Uteroglobin mRNA may be an useful marker for the differentiation of various endometrial epithelial cell populations.

Morphological and immunohistochemical differentiation patterns of rabbit uterine epithelium in vitro

We describe morphological and immunohistochemical changes of uterine epithelium from immature rabbits in vitro in response to hormonal treatments, using a matrix-coated semipermeable filter. These investigations were compared to in vivo studies of uterine epithelium from immature rabbits treated with estrogen and/or progesterone. In vitro, polarization of the epithelium seems to be best developed under progesterone dominance, and the pattern of cell organelles is similar to those seen in vivo. Two types of apical protrusions could be observed in cultures treated with progesterone, some shaped like domes, containing cell organelles, and some irregular in shape with small lucent vesicles. Both types of apical differentiation are typical for the in vivo situation. In vitro, estrogen leads to a more pseudostratified growth pattern of the cells. They develop apical protrusions with big vesicles probably containing mucin, as in vivo. Treatment with both steroid hormones leads to a heterogeneous response of the uterine epithelial cells in culture, some cells responding more to the estrogen, others to the progesterone whereas in vivo the progesterone-dominant features are obvious. Immunohistochemistry of uteroglobin in monensin-treated cultures gives evidence for uteroglobin secretion in all cultures, but to a lesser extent in the untreated, and this is strongly increased in cultures treated with estrogen and progesterone. These results correspond to observations made in vivo. This in vitro cell culture method seems therefore to provide a useful model for investigating the regulatory mechanisms of sexual steroid hormones and the cell biology of uterine receptivity.

Uteroglobin in the developing rabbit conceptus in vivo and in vitro

Uteroglobin (UGL) was measured in day-4 to day-10 rabbit conceptuses by a competitive ELISA. Levels in blastocyst fluid, tissues, coverings and in the early fetus were determined separately. The total amount of UGL increased from 18.4 ng to 6.8 micrograms per conceptus. The UGL content of individual day-6 blastocysts was studied in vitro. Culturing was carried out up to 60 h in Ham's F10 medium with polyvinylpyrrolidone as macromolecular component, with and without progesterone, and with progesterone plus estradiol. UGL was determined in the blastocyst fluids, tissues with coverings and in the culture media. After labelling with [35S]-methionine, protein patterns of total blastocysts and of culture media were analysed by two-dimensional gel electrophoresis and fluorography. The morphology of cultured blastocysts was examined by electron microscopy. During 60 h of culture, the blastocysts expanded in diameter by 84%, and released 19% of their initial UGL content into the medium, independent of the hormonal substitution. Neither de novo synthesis, nor degradation of UGL was found: the protein remained unlabelled in fluorography, and its total quantity was not significantly different from that of non-cultured controls. Trophoblast, endoderm and embryoblast cells showed well preserved cell organelles and intercellular junctions, while the morphological differentiation of the germ layer was inhibited.

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

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 25 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.

Variable expression of the uteroglobin gene following the administration of norethisterone and its A-ring reduced metabolites

Enzyme-mediated A-ring reduction of norethisterone (NET) results in the transformation of a molecule with potent intrinsic progestational activity into neutral derivatives with estrogen-like effects. To ascertain whether these structural modifications of NET are able to modify the uteroglobin (U) gene (G) expression, a series of experiments assessing the UG products after the administration of NET and its reduced A-ring metabolites were conducted in prepubertal female rabbits. Synthesis of endometrial uteroglobin and its specific mRNA were studied in animals following the administration of NET, 5 alpha-dihydro NET,3 beta,5 alpha-tetrahydro NET and progesterone. Animals treated with either estradiol or vehicle alone served as controls. The uteroglobin content in uterine flushings and cytosols was determined by immunodiffusion and polyacrilamide gel electrophoresis techniques and by a specific double-antibody radioimmunoassay, while the U mRNA synthesis was assessed by its molecular hybridization to [alpha 32P]d-ATP uteroglobin cDNA. NET induced a significant increase of the uterine content of uteroglobin similar to that observed with progesterone with a simultaneous increase on U mRNA synthesis. On the contrary, 5 alpha-NET and 3 beta,5 alpha-NET induced very little, if any uteroglobin synthesis with a concomitantly low U mRNA production as compared with NET; thus exhibiting a similar effect to that observed in estradiol-treated animals. The overall results were interpreted as demonstrating that the enzyme mediated structural changes of NET which occur at the target organs induce variable expression of the uteroglobin gene. The data indicate that the rabbit uteroglobin gene products are suitable molecular markers to evaluate the hormonal potency of contraceptive synthetic progestins and their derivatives.

Uptake of tritiated uteroglobin by the endometrium of the rabbit during peri-implantation

Uteroglobin, labelled with N-succinimidyl-(2-3-3H)-propionate, was applied in vivo for 3 h to pregnant rabbit uteri 7 and 9 days after mating. Light- and electron-microscopic autoradiographs showed that the endometrial epithelium, both ciliated and non-ciliated cells, is able to take up 3H-uteroglobin, however, with differing intensity. Large areas of labelling were found in the luminal epithelium, whereas the glandular epithelium contained fewer silver grains. Moreover, intensively labelled single cells or symplasms occurred in both luminal and glandular epithelium. They were identified as degenerating or dead cells. After internalization by pinocytosis or phagocytosis, the tritiated uteroglobin was observed in multivesicular bodies or in lysosomes with floccular content. Later, radioactivity was either found within residual bodies or distributed throughout the entire epithelium and the subepithelial stroma, i.e., the silver grains could no longer be assigned to specific cell organelles.

Macromolecular transport in rabbit blastocysts: evidence for a specific uteroglobin transport system

Though uterine proteins are found within the blastocoel of the rabbit blastocyst, the mechanisms involved in protein entry into the blastocoel have not been studied. To investigate potential avenues of protein entry into the blastocoel, we have monitored uptake of a fluorescent, fluid-phase marker (lucifer yellow) into the rabbit blastocyst trophectodermal cell. In addition, we have measured the transtrophectodermal permeabilities of several uterine proteins (uteroglobin (UTG), rabbit serum albumin, rabbit IgG), and radiolabeled fluid-phase markers (sucrose, polyethylene glycol, dextran) in the 6- and 7-day post-coitus rabbit blastocyst. Extrablastocoelic lucifer yellow (LY) was rapidly endocytosed by the trophectodermal cell and was subsequently trapped in a perinuclear compartment for at least 30 min after removal of the extracellular dye. The slow rate of LY turnover within the endocytic compartments implies that the rate of fluid-phase transcytosis was negligible. Permeability coefficients of the fluid-phase markers and proteins, with the exception of UTG, decreased with increasing molecular weight of each compound tested. These data are consistent with the conclusion that these compounds traverse the trophectoderm via a 'leak' pathway, as opposed to a transcytotic pathway. In contrast, permeability of 125I-UTG when compared to the other compounds, was 10-fold greater than would be predicted based on its molecular weight. Furthermore, the flux of radioiodinated UTG displayed saturation kinetics with a Km of 19.5 micrograms/ml and a Vmax of 132 ng.cm-2.h-1. Sodium dodecylsulfate-polyacrylamide gel electrophoresis demonstrated that the radioiodinated protein recovered from the blastocoel was of a lower molecular weight than native UTG and was not immunoreactive with goat anti-UTG antibody. Our data are consistent with the idea that UTG is transported across the trophectoderm by a receptor-mediated system, and UTG is modified intracellularly during transport to a protein of a lower molecular weight.

Expression of a uteroglobin-like protein in human prostate

Phospholipase A2 (PLA2) is a key enzyme that initiates the arachidonic acid cascade responsible for the synthesis of prostaglandins and leukotrienes, compounds well known for their inflammatory properties. Inhibition of this enzyme may modulate prostaglandin and leukotriene tissue levels. Uteroglobin is a potent PLA2 inhibitor found in rabbit uterus, prostate, seminal vesicle, and tracheobronchial tree. Tissue from ten human patients undergoing prostatectomy was examined for presence of a uteroglobin-like protein. Seven patients underwent transurethral resection and three had an open prostatectomy. Preoperative diagnosis in nine of the 10 patients was benign prostatic hypertrophy. One suspected, poorly differentiated, adenocarcinoma was confirmed and one unsuspected, well differentiated, adenocarcinoma was discovered. Specimens were submitted for Western blot, electron microscopy with immunogold staining, radioimmunoassay, and immunofluorescence. Six patients had evidence of uteroglobin-like protein, three with high levels (greater than or equal to 1000 pg./mg. protein), two with moderate levels (75 to 250 pg.), one with a low level (less than or equal to 75 pg.). Uteroglobin-like protein was present in all three patients who underwent open prostatectomy and in three of the seven patients with transurethral resections. The uteroglobin-like protein level was 2.5 to five times greater in both prostatic utricle specimens. All four assays corroborated these results. Because rabbit uteroglobin coats sperm and masks spermatic antigenicity in the rabbit female genital tract, this report of biochemical and immunological evidence for uteroglobin-like protein in the human prostate may have implications for human male fertility.

Uteroglobin as progesterone-binding protein in the preimplantation uterine epithelium of the rabbit: histochemical studies

[3H] progesterone was injected into the uterine lumen of rabbits toward the end of preimplantation period (162 h post coitum). Light-microscopic autoradiography showed accumulation of label in single cell groups of the uterine epithelium. Fluorographs of thin layer chromatograms of steroid extracts indicated the metabolization of progesterone in the uterine tissue. Incubation of uterine sections with fluorescein isothiocyanate-conjugated progesterone-rabbit serum albumin revealed binding sites for this reagent: 162 h post coitum, staining was also localized in single cell groups of the uterine epithelium. Pretreatment with a monospecific antiserum showed uteroglobin to be the binding protein.

Testosterone induces the expression of the uteroglobin gene in rabbit epididymis

Uteroglobin was characterized in the rabbit epididymis by radioimmunoassay and electrophoretic determinations, as well as by analysis of its mRNA by means of 'Northern blot' and nuclease-S1 mapping. Treatment of sexually immature rabbits with testosterone during 5 days increased up to 8-fold the concentrations of both uteroglobin and its mRNA in the epididymis. The amounts of beta-tubulin mRNA, measured as reference, remained unchanged after the hormonal treatment. The synthesis of uteroglobin occurred mainly in the middle region of the epididymis, progressively decreasing toward the distal part of the organ. Uteroglobin was not detected in the testis by radioimmunoassay. The results are discussed in relation to a possible role of uteroglobin in the reproductive functions.

Ultrastructural and kinetic studies on uteroglobin secretion in the uterus and oviduct of the pseudopregnant rabbit

The intracellular localization of uteroglobin, a progesterone-induced protein, was studied in uterus and oviduct by means of immunoelectron microscopy with the protein A-gold technique. In the uterus, uteroglobin was synthesized in the columnar epithelium of the endometrium where most of the cells were immunoreactive. The protein was localized mainly in small secretory granules which were seen in the process of release into the uterine lumen. The luminal microvilli were also heavily stained. In the oviduct, the secretory cells contained large immunoreactive granules at the apical zone, some of which were observed while discharging into the lumen. Within these secretory granules, uteroglobin accumulated particularly in lens-shaped patches at the periphery of the granules. In vitro kinetic studies on the secretion of newly synthesized uteroglobin indicated that the ability to store uteroglobin is greater in the oviduct than in the uterus; however, the rate of uteroglobin secretion is greater in the uterus than in the oviduct. Thus, there appears to be a good correlation between the microscopic and the functional observations.

Uteroglobin production in the pseudopregnant rabbit uterus. Immunohistochemical studies

Uteroglobin, a secretory protein of rabbit uterine epithelium, was localized by the direct immunoperoxidase method in control and hCG-induced pseudopregnant rabbits. In control rabbits, uteroglobin was confined to the apical cytoplasm of nearly all cells of the endometrial epithelium. The induction of pseudopregnancy resulted in a pronounced continuing increase, through 4 days post-hCG administration, in the absolute number of epithelial cells engaged in uteroglobin synthesis. Furthermore, the endoplasmic reticulum was more intensely stained for uteroglobin than in the epithelial cells of control rabbit endometrium. Thus, the increased production of uteroglobin, in response to hormonal stimulation, appears to be achieved both through an increase in the amount of uteroglobin synthesized by a given cell as well as by an increase in the number of cells involved in uteroglobin synthesis. Concurrent with the increase in the number of cells synthesizing uteroglobin, an increase in the number of unstained cells first appeared at the second day of pseudopregnancy, during the period of maximal epithelial proliferation. However, within those cells containing uteroglobin on the second day following injection with hCG, most staining was limited to the perinuclear membrane. At various times following hCG administration, a number of scattered cells, intensely stained for uteroglobin, were observed in the uterine epithelium. Based upon ultrastructural studies, failure to exclude trypan blue, and the presence of intra-mitochondrial uteroglobin, they were identified as either dead or dying cells.

Immunocytochemical localization of uteroglobin in the rabbit endometrium

Uteroglobin, the progesterone dependent pregnancy-characteristic endometrial protein in the rabbit, is found within the endometrial epithelium on the fourth and sixth day of pregnancy at the electron-microscopic level by use of the immunoperoxidase technique and a specific anti-uteroglobin serum from the sheep. As known from earlier studies, uteroglobin is the predominant protein synthesized of the endometrial secretion. In the present study, it is localized exclusively in the non-ciliated epithelial cells. A common route of secretory proteins within these cells is observed by uteroglobin labelling: rough endoplasmatic reticulum----Golgi complex----condensing vesicles----secretory products. Uteroglobin occurs in small vesicles on the trans-face of the Golgi complex, and in addition beneath the apical plasma membrane where it appears in membrane-bound vesicles, which apparently are extruded into the uterine lumen. Most of the uteroglobin is located in the luminal secretion. The distribution of intracellular uteroglobin is found only in cells of the basal endometrial gland, adjacent to the myometrium. The cytoplasm of uterine epithelial cells facing the cavum does not show uteroglobin reaction products.

Ultrastructural localization of uteroglobin immunoreactivity in rabbit lung and endometrium, and rat ventral prostate

Recent biochemical studies have demonstrated amino acid sequence homologies between uteroglobin from rabbit endometrium and prostatic binding protein from rat ventral prostate. We have studied the ultrastructural distribution of uteroglobin-immunoreactive material in rabbit lung and endometrium and rat ventral prostate using an uteroglobin antibody raised in guinea pigs. Secretory granules of bronchiolar Clara cells, endometrial non-ciliated cells and rat prostate secretory cells gave a positive immunoreaction when this antibody was used. The results indicate a close relationship of immunoreactive epitopes of proteins present in those secretory cells. The functional properties of these proteins (glycoproteins, steroid binding, androgen-dependent secretion) suggest a close functional relationship, for instance a surface action such as coating, capping, masking or lubrication.

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.

Genital tract proteins in the male rabbit: I. Localization of uteroglobin

Uteroglobin synthesis in reproductive and non-reproductive tissues of male and female rabbit was screened by means of double-diffusion tests and immunohistochemical studies. Immunoprecipitates were observed when homogenates of male accessory were incubated with a monospecific antiserum against uteroglobin; in the female the antigen occurred in the uterine secretion and in homogenates of the oviduct, six days post coitum. In nonreproductive tissue, the antigen appeared both in the male and in the female, in the homogenate of trachea and lung. The immunofluorescence technique exhibited the paraprostate gland as the site of synthesis of uteroglobin in the male genital tract. Moreover, the distribution of the fluorescence within the cells was identical to the distribution observed in the female genital tract.

Uteroglobin: a model for the sutyd of progesterone action in mammals

Uteroglobin, a progesterone-binding protein, is expressed in several organs, principally endometrium and lung, of the rabbit and other rodents. The phasic activation of the uteroglobin gene in the endometrium during early pregnancy is regulated by progesterone, which contrasts with the constitutive, nonregulated expression of this gene in the lung. Thus, uteroglobin provides a useful model for the study of differential gene regulation by hormones as well as for the study of steroid-protein interactions.

In vitro binding to an in vivo effect on the cytosol and nuclear progesterone receptors of various progestins, and their relationship to synthesis of uteroglobin in rabbit uterus

In vitro binding affinities of various progestins to cytosol and nuclear progesterone receptors of rabbit uterus were determined and correlated with the biological potency of these steroids. In addition, cytosol and nuclear progesterone receptor levels were measured after a 5-day administration of different progestins (0.5 mg/kg daily) with variable biologic activities. The receptor levels were compared with the biological response; the induction of uteroglobin synthesis. Cytosol and nuclear progesterone receptors had identical steroid binding properties (r = 0.98). The correlation between the in vitro binding affinity (cytosol or nuclear) and the in vivo biologic activity of the steroids was good (r = 0.73). After a 5-day treatment with progestins, the nuclear receptor concentration correlated n an inverse manner (r = -0.84) with the uterine fluid uteroglobin concentration. A similar, but slightly weaker correlation (r = -0.81) was also found for the cytosol receptor content and uteroglobin secretion. These data indicate that not only nuclear, but also cytosol progesterone receptor levels decrease in the rabbit uterus during chronic hormone action. Decline in the nuclear progesterone receptor content seemed to occur during treatment with all progestational steroids, while only progestins with high biological potency were capable of decreasing the cytosol receptor content.

Hormonal control of uteroglobin secretion and preuteroglobin mRNA content in rabbit endometrium

The cellular content of preuteroglobin mRNA in endometrium was measured by molecular hybridization to preuteroglobin cDNA, and compared with uteroglobin content in the uterine secretion as determined by radioimmunoassay. The following results were obtained. (1) A single injection of either estradiol or progesterone leads to a rapid accumulation of preuteroglobin mRNA in the endometrium, but has no effect on the cellular content of preuteroglobin mRNA in the lung. (2) The effect of progesterone on uteroglobin on secretion parallels its influence on preuteroglobin mRNA levels, but estradiol has a more pronounced effect on the mRNA content than on uteroglobin secretion. (3) 5 days after priming with estradiol, a single injection of progesterone leads to the accumulation of preuteroglobin mRNA sequences without measurable lag phase, whereas a lag period is found if progesterone is administered earlier after estradiol treatment. (4) In the endometrium of pseudopregnant rabbits there are around 10 000 molecules of preuteroglobin mRNA per epithelial cell as compared with 300 in control estrous rabbits, and 1000-2000 in animals treated with estradiol alone. (5) Following maximal induction, the apparent half-life of uteroglobin and its mRNA are inversely influenced by estrogens: estradiol accelerates the disappearance of uteroglobin from the uterine secretion, and retards the decay of preuteroglobin mRNA sequences in endometrium.

Synthesis and characterization of a DNA complementary to pre-uteroglobin mRNA

Uteroglobin, a progesterone-induced uterine protein of the rabbit, is synthesized in cell-free systems as a precursor containing 21 additional amino-acids at its N-terminal end. The mRNA for pre-uteroglobin has been purified from the membrane-bound polysomes of induced endometrium and used as template for the synthesis of a full copy complementary DNA. Final purification of the cDNA was based on hybridization to the template mRNA up to a low value of r0t (0.01 M . s) and digestion of the non-hybridized cDNA by S1 nuclease. A comparison of the hybridization kinetics of the pre-uteroglobin cDNA and rabbit globin cDNA to their respective templates indicates a nucleotide sequence complexity of 650 for pre-uteroglobin mRNA, in agreement with the values obtained by sucrose gradient centrifugation and polyacrylamide gel electrophoresis in formamaide. The melting temperature of the hybrids of pre-uteroglobin cDNA to its template reflects the absence of mismatched sequences. This cDNA has been used to quantify pre-uteroglobin mRNA sequences in the endometrial RNA from control animals and from animals treated sequentially with estradiol and progesterone. In agreement with the induction of uteroglobin-synthesizing activity, there is a dramatic increase in the uterine content of pre-uteroglobin mRNA after hormonal treatment. Part of this effect can be accounted for by hormonally induced cell proliferation. When expressed on a DNA basis there is a 50--100-fold increase in the cellular content of pre-uteroglobin mRNA following hormonal treatment.

Uteroglobin in the rabbit. II. Intracellular localization in the uterus after hormone treatment

Rabbit uterine uteroglobin (UGL) was studied by electrophoretic and immunological methods following normal copulation, after ovariectomy and progesterone treatment, 17beta-oestradiol and combined progesterone treatment, 17 beta-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 domonstrated 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. 17beta-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 beta-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 beta-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.