Interaction of estrogen and progesterone in chick oviduct development. I. Antagonistic effect of progesterone on estrogen-induced proliferation and differentiation of tubular gland cells

Overview of Avian Sex Reversal

Sex determination and differentiation are processes by which a bipotential gonad adopts either a testicular or ovarian cell fate, and secondary sexual characteristics adopt either male or female developmental patterns. In birds, although genetic factors control the sex determination program, sex differentiation is sensitive to hormones, which can induce sex reversal when disturbed. Although these sex-reversed birds can form phenotypes opposite to their genotypes, none can experience complete sex reversal or produce offspring under natural conditions. Promising evidence indicates that the incomplete sex reversal is associated with cell autonomous sex identity (CASI) of avian cells, which is controlled by genetic factors. However, studies cannot clearly describe the regulatory mechanism of avian CASI and sex development at present, and these factors require further exploration. In spite of this, the abundant findings of avian sex research have provided theoretical bases for the progress of gender control technologies, which are being improved through interdisciplinary co-operation and will ultimately be employed in poultry production. In this review, we provide an overview of avian sex determination and differentiation and comprehensively summarize the research progress on sex reversal in birds, especially chickens. Importantly, we describe key issues faced by applying gender control systems in poultry production and chronologically summarize the development of avian sex control methods. In conclusion, this review provides unique perspectives for avian sex studies and helps scientists develop more advanced systems for sex regulation in birds.

Post-hatch changes in the histological structure of the oviduct and associated 17β-estradiol profiles in guinea hens (Numida meleagris)

There is a limited data available on the biology of guinea fowls. The objective of this study was to document post-hatch histological and stereological changes in the oviducts of 56 guinea hens and associated 17β-estradiol profiles until 32 wk of age and to explore changes in the oviducal mucosal fold as an index of oviducal growth. Mucosal folds in all regions of the oviduct increased significantly (P < 0.0001) from 4 to 28 wk of age. Concentrations of plasma 17β-estradiol increased from 20 to 28 wk of age, when it stabilized. Mucosal folds in the oviducts of sexually active hens were highest in the uterine region and lowest in the infundibular lip. Intercorrelations among 17β-estradiol concentration, height of mucosal folds, and oviducal weight were strong and positive in these birds. Most of the oviduct epithelium consisted of pseudostratified columnar ciliated epithelium. Both the height of oviducal folds and peripheral estradiol concentrations increased significantly from 20 to 28 wk of age, which confirms the role of estradiol in oviducal growth in the avian species. The height of oviducal mucosal folds appears to be a good measure of oviducal growth.

In ovo treatment with an estrogen receptor alpha selective agonist causes precocious development of the female reproductive tract of the American alligator (Alligator mississippiensis)

The molecular signaling processes involved the differentiation of the Müllerian duct (MD) into the female reproductive tract, or oviduct, in non-mammalian vertebrates are not well understood. Studies in mammals and birds indicate that steroid hormones play a role in this process, as the embryonic MD has been shown to be vulnerable to exogenous estrogens and progestins and environmental endocrine disrupting contaminants. In a previous study, developmental treatment with an estrogen receptor α (ERα) agonist, 4,4',4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT), induced significant enlargement of the MD in alligator embryos incubated at a male-producing temperature, which was not observed in embryos treated with an estrogen receptor β (ERβ) agonist, 7-bromo-2-(4-hydroxyphenyl)-1,3-benzoxazol-5-ol (WAY 200070), or with 17β-estradiol (E₂). In order to understand the role of estrogen signaling in female alligator oviduct development, we incubated eggs at a female-producing temperature and treated them with E₂ and these ER selective agonists, PPT and WAY 200070, just prior to the thermosensitive window of sex determination. At stage 27, one stage prior to hatching, PPT induced significant enlargement of the MD with precocious development of secretory glands and connective tissue differentiation similar to characteristics of mature adult oviduct. PPT treatment in ovo increased mRNA expression of ERβ, progesterone receptor, androgen receptor and insulin-like growth factor 1 in MD at stage 27, while expression of ERα was decreased. Neither WAY 200070 nor E₂ treatment induced these effects seen in PPT-treated MD. The results of this study provide insight into the critical factors for healthy reproductive system formation in this sentinel species, although further investigation is needed to determine whether the observed phenomena are directly due to selective stimulation of ERα or related to some other aspect of PPT treatment.

Cracking the egg: An insight into egg hypersensitivity

Hypersensitivity to the chicken egg is a widespread disorder mainly affecting 1-2% of children worldwide. It is the second most common food allergy in children, next to cow's milk allergy. Egg allergy is mainly caused by hypersensitivity to four allergens found in the egg white; ovomucoid, ovalbumin, ovotransferrin and lysozyme. However, some research suggests the involvement of allergens exclusively found in the egg yolk such as chicken serum albumin and YGP42, which may play a crucial role in the overall reaction. In egg allergic individuals, these allergens cause conditions such as itching, atopic dermatitis, bronchial asthma, vomiting, rhinitis, conjunctivitis, laryngeal oedema and chronic urticaria, and anaphylaxis. Currently there is no permanent cure for egg allergy. Upon positive diagnosis for egg allergy, strict dietary avoidance of eggs and products containing traces of eggs is the most effective way of avoiding future hypersensitivity reactions. However, it is difficult to fully avoid eggs since they are found in a range of processed food products. An understanding of the mechanisms of allergic reactions, egg allergens and their prevalence, egg allergy diagnosis and current treatment strategies are important for future studies. This review addresses these topics and discusses both egg white and egg yolk allergy as a whole.

Differential expression of secreted phosphoprotein 1 in response to estradiol-17β and in ovarian tumors in chickens

Secreted phosphoprotein 1 (SPP1), a highly phosphorylated protein containing a polyaspartic acid sequence and a conserved RGD motif, plays important roles in physiological processes such as inflammatory responses, calcification, organ development, immune cell function and carcinogenesis. Results of the present study indicate expression of SPP1 mRNA in various organs such as oviduct, small intestine and kidney from chickens, particularly in the glandular epithelium (GE) of the shell gland and, to a lesser extent, in luminal epithelium (LE) of the infundibulum and magnum, and GE of the isthmus of the oviduct. We determined that DES (diethylstilbestrol, a synthetic nonsteroidal estrogen) decreases SPP1 expression in the oviduct and that SPP1 mRNA and protein are significantly more abundant in GE of ovarian endometrioid carcinoma, but not the other cancerous and normal ovaries of hens. Further, microRNA-140 was discovered to influence SPP1 expression via its 3'-UTR which suggests that post-transcriptional regulation influences SPP1 expression in chickens. Collectively, results of this study indicate that SPP1 is novel in that its expression is down-regulated by estrogen in epithelial cells of the chicken oviduct and that it is up-regulated in chicken ovarian endometrioid tumor that could be used for monitoring effects of therapies for this disease in laying hens.

Tissue specific expression and estrogen regulation of SERPINB3 in the chicken oviduct

Serine protease inhibitors (SERPINs) comprise the largest superfamily of protease inhibitors and appear to be ubiquitously expressed in a variety of species. Of these, squamous cell carcinoma antigen 1 (SCCA1), also known as a SERPINB3, was first identified in squamous cell carcinoma tissue from the cervix of women. However, there is little known about the expression and hormonal regulation of SERPINB3 in chickens. Therefore, the avian SERPINB3 gene was compared with those of other species with respect to structure, phylogenetic evolution and tissue- and cell-specific expression in hens. Chicken SERPINB3 has moderate homology to mammalian SERPINB3 proteins (36-47%). Of particular note, SERPINB3 mRNA was most abundant in the chicken oviduct and cell-specific expression was in glandular (GE) and luminal (LE) epithelial cells of the oviduct of laying hens. Treatment of young chicks with DES (diethylstilbestrol, a synthetic nonsteroidal estrogen) induced SERPINB3 mRNA and protein in GE and LE, but not in other cell types of the oviduct. Western blot analyses determined that immunoreactive SERPINB3 protein was also increased by DES in LE and GE of the oviduct of chicks. Collectively, these results indicate that SERPINB3 is an estrogen-induced gene expressed only in LE and GE of the chicken oviduct and implicate SERPINB3 in regulation of oviduct development and egg formation.

Differential expression of alpha 2 macroglobulin in response to dietylstilbestrol and in ovarian carcinomas in chickens

BACKGROUND

Alpha 2 macroglobulin (A2M; also known as ovostatin), a homotetrameric protein with four disulfide-linked subunits, has the unique feature of inactivating/inhibiting most known proteases including serine-, threonine-, cysteine-, aspartic- and metalloproteases. In chickens, A2M has been identified and characterized biochemically, but little is known of its functional role(s) in the oviduct, hormonal regulation of expression or its expression in ovarian carcinomas in chickens. Therefore, we investigated estrogen regulation of A2M gene expression during development of the chicken oviduct, and its expression in normal and cancerous ovaries from chickens.

METHODS

To determine tissue-specific expression of A2M in chickens, we collected various organs from male and female chickens and performed RT-PCR analyses. To examine A2M gene expression in the oviduct of 1-week-old female chicks that received a subcutaneous implant of 15 mg DES in the abdominal region for 20 days, we performed RT-PCR, qPCR and in situ hybridization analyses using cDNAs from control- (n=5) and DES-treated oviducts (n=5), and then each segment of the oviduct from DES-treated chicks. To determine if A2M is a biomarker of ovarian cancer in hens, we collected cancerous (n=10) ovaries from a total of 136 chickens which had completely stopped egg-laying and performed RT-PCR and in situ hybridization analyses.

RESULTS

We found that A2M is most abundant in the chicken oviduct, specifically luminal (LE) and glandular epithelia (GE), but it was not detected in any other tissues of either sex. We then determined that DES (dietylstilbestrol, a synthetic nonsteroidal estrogen) increased A2M mRNA only in LE and GE of the oviduct of chicks. Further, expression of A2M was most abundant in GE of endometrioid adenocarcinoma of cancerous, but not normal ovaries of hens.

CONCLUSIONS

Collectively, results of the present study indicate that A2M is novel estrogen-stimulated gene expressed in LE and GE of the chicken oviduct and may be used for monitoring effects of therapies for ovarian cancer in laying hens.

Structural and histological characterization of oviductal magnum and lectin-binding patterns in Gallus domesticus

BACKGROUND

Although chicken oviduct is a useful model and target tissue for reproductive biology and transgenesis, little is known because of the highly specific hormonal regulation and the lack of fundamental researches, including lectin-binding activities and glycobiology. Because lectin is attached to secreted glycoproteins, we hypothesized that lectin could be bound to secretory egg-white proteins, and played a crucial role in the generation of egg-white protein in the oviduct. Hence, the purpose of this study was to investigate the structural, histological and lectin-binding characteristics of the chicken oviductal magnum from juvenile and adult hens.

METHODS

The oviductal magnums from juvenile and adult hens were prepared for ultrastructural analysis, qRT-PCR and immunostaining. Immunohistochemistry of anti-ovalbumin, anti-ESR1 and anti-PGR, and mRNA expression of egg-white genes and steroid hormone receptor genes were evaluated. Lectin histochemical staining was also conducted in juvenile and adult oviductal magnum tissues.

RESULTS

The ultrastructural analysis showed that ciliated cells were rarely developed on luminal surface in juvenile magnum, but not tubular gland cells. In adult magnum, two types of epithelium and three types of tubular gland cells were observed. qRT-PCR analysis showed that egg-white genes were highly expressed in adult oviduct compared with the juvenile. However, mRNA expressions of ESR1 and PGR were considerably higher in juvenile oviduct than adult (P < 0.05). The immunohistochemical analysis showed that anti-ovalbumin antibody was detected in adult oviduct not in juvenile, unlikely anti-ESR1 and anti-PGR antibodies that were stained in both oviducts. In histological analysis, Toluidine blue was stained in juvenile and adult oviductal epithelia, and adult tubular glands located in the outer layer of oviductal magnum. In contrast, PAS was positive only in adult oviductal tubular gland. Lectins were selectively bound to oviductal epithelium, stroma, and tubular gland cells. Particularly, lectin-ConA and WGA were bound to electron-dense secretory granules in tubular gland.

CONCLUSIONS

The observation of ultrastructural analysis, mRNA expression, immunohistochemistry and lectin staining showed structural and physiological characterization of juvenile and adult oviductal magnum. Consequently, oviduct study could be helped to in vitro culture of chicken oviductal cells, to develop epithelial or tubular gland cell-specific markers, and to understand female reproductive biology and endocrinology.

Calcium transport in strongly calcifying laying birds: mechanisms and regulation

Birds that lay long clutches (series of eggs laid sequentially before a "pause day"), among them the high-producing, strongly-calcifying Gallus gallus domesticus (domestic hen) and Coturnix coturnix japonica (Japanese quail), transfer about 10% of their total body calcium daily. They appear, therefore, to be the most efficient calcium-transporters among vertebrates. Such intensive transport imposes severe demands on ionic calcium (Ca2+) homeostasis, and activates at least two extremely effective mechanisms for Ca2+ transfer from food and bone to the eggshell. This review focuses on the development, action and regulation of the mechanisms associated with paracellular and transcellular Ca2+ transport in the intestine and the eggshell gland (ESG); it also considers some of the proteins (calbindin, Ca2+ATPase, Na+/Ca2+ exchange, epithelial calcium channels (TRPVs), osteopontin and carbonic anhydrase (CA) associated with this phenomenon. Calbindins are discussed in some detail, as they appear to be a major component of the transcellular transport system, and as only they have been studied extensively in birds. The review aims to gather old and new knowledge, which could form a conceptual basis, albeit not a completely accepted one, for our understanding of the mechanisms associated with this phenomenon. In the intestine, the transcellular pathway appears to compensate for low Ca2+ intake, but in birds fed adequate calcium the major drive for calcium absorption remains the electrochemical potential difference (ECPD) that facilitates paracellular transport. However, the mechanisms involved in Ca2+ transport into the ESG lumen are not yet established. In the ESG, the presence of Ca2+-ATPase and calbindin--two components of the transcellular transport pathway--and the apparently uphill transport of Ca2+ support the idea that Ca2+ is transported via the transcellular pathway. However, the positive (plasma with respect to mucosa) electrical potential difference (EPD) in the ESG, among other findings, indicates that there may be major alternative or complementary paracellular passive transport pathways. The available evidence hints that the flow from the gut to the ESG, which occurs during a relatively short period (11 to 14 h out the 24- to 25.5-h egg cycle), is primarily driven by carbonic anhydrase (CA) activity in the ESG, which results in high HCO3(-) content that, in turn, "sucks out" Ca2+ from the intestinal lumen via the blood and ESG cells, and deposits it in the shell crystals. The increased CA activity appears to be dependent on energy input, whereas it seems most likely that the Ca2+ movement is secondary, that it utilizes passive paracellular routes that fluctuate in accordance with the appearance of the energy-dependent CA activity, and that the level of Ca2+ movement mimics that of the CA activity. The on-off signals for the overall phenomenon have not yet been identified. They appear to be associated with the circadian cycle of gonadal hormones, coupled with the egg cycle: it is most likely that progesterone acts as the "off" signal, and that the "on" signal is provided by the combined effect of an as-yet undefined endocrine factor associated with ovulation and with the mechanical strain that results from "egg white" formation and "plumping". This strain may initially trigger the formation of the mammillae and the seeding of shell calcium crystals in the isthmus, and thereafter initiate the formation of the shell in the ESG.

Ontogenic variations in the content and distribution of progesterone receptor isoforms in the reproductive tract and brain of chicks

Progesterone participates in the regulation of several functions in chicks such as ovulation, gonadal differentiation, and sexual and nesting behaviors. Many progesterone actions are mediated by specific intracellular receptors (PR) which are ligand-induced transactivators. Two PR isoforms that are functionally distinct in their ability to activate genes and regulate distinct physiological processes have been described in chicks: a full length form PR-B and the N-terminally truncated one PR-A which lacks the amino-terminal 128 amino acids of PR-B. PR isoforms have been detected in several tissues of both the adult and the embryo chick such as brain, ovary and oviduct. PR isoforms expression ratio varies among progesterone target tissues and under different hormonal and environmental conditions such as those presented during avian sexual maturity and the seasons of the year. These data let us to conclude that progesterone actions in brain, ovary, and oviduct highly depend on PR isoforms expression pattern and regulation.

Estrogen action: revitalization of the chick oviduct model

Despite decades of investigation, the molecular pathways triggered by estrogen that lead to tissue-specific cell proliferation, differentiation and survival are only superficially understood. If we are to modulate the actions of estrogen selectively in these processes, continued investigation using biologically relevant models is essential. The chick oviduct emerged as an early model for investigating the mechanism of action of steroid hormones because of its exquisite responsiveness to them. Unfortunately, because of experimental limitations, this model has been neglected in the past decade. Reviving this model has become intellectually attractive and technically feasible.

Progesterone receptor in the liver and oviduct of the lizard Podarcis sicula

In this paper we report the presence of a (3)H-Progesterone ((3)H-P) binding moiety, which has the characteristics of a true receptor, in the liver of the female of the lizard Podarcis sicula. (3)H-P binding studies show the presence of one type of binding site with an average Kd value of 6.2 +/- 2.0 nM in the cytoplasm and 6.3 +/- 1.1 nM in the nucleus. Competition experiments showed that progesterone (P) was the best competitor, while testosterone, deoxycorticosterone (DOC), corticosterone, 17 alpha-hydroxyprogesterone; R5020; RU486 and RU26988-5 were poor competitors. We have also investigated the immunological characteristics of progesterone receptor (PR) in both the liver and the oviduct of Podarcis sicula, by Western blotting using the monoclonal antibody PR22 raised against the PR isoforms A and B of chicken. One imunoreactive band of about 70 kDa was detected in cytoplasmic and nuclear extracts of both the liver and the oviduct. PR immunoreactivity was present in the liver during the quiescent phase. In the oviduct PR immunoreactivity increased from the recovery to the full grown phase. P treatment of estrogen-primed females did not affect the presence of PR in the liver, while brought about a PR increase in the oviduct. This study suggests that PR is expressed differently in the liver and the oviduct of Podarcis sicula throughout the reproductive cycle. PR might fulfill different requirements in relation to the different physiological functions of the tissue during the reproductive cycle.

A estradiol-17beta receptor in the reproductive system of the female of Octopus vulgaris: characterization and immunolocalization

In this study, for the first time we have identified an estradiol-17beta receptor (ER) in the reproductive system of the female of Octopus vulgaris. Scatchard analysis revealed that one binding component with high affinity and low capacity for the ligand was present in the cytosol, but not in the nuclear extract of the ovary and the oviduct. A steroid specificity competition assay showed that 3H-estradiol-17beta binding activity showed a preference for estradiol-17beta. DNA-cellulose chromatography confirmed the presence of one 3H-estradiol-17beta binding component. By using antibodies anti ER (578-595), we have localized by Western blotting one band of about 70 kDa. ER immunoreactivity has been localized in the nuclei of the follicle cells of the ovary, in the nuclei of the epithelium lining the proximal portion of the oviduct and in the nuclei, and in the cytoplasm of the inner region of the oviducal gland and in the cytoplasm of the outer region of the oviducal gland. These data, taken together, provide evidence that in Octopus vulgaris the ER has biochemical and immunohistochemical characteristics resembling those of ER in vertebrates.

Posthatch oral estrogen exposure impairs adult reproductive performance of zebra finch in a sex-specific manner

We determined whether short-term, posthatch oral exposure to estradiol benzoate (EB) or the industrial surfactant octylphenol (OP) could impair the reproductive performance of zebra finches. If so, naturally occurring phytoestrogens and xenoestrogens might influence reproduction in wild populations. Chicks were given oral administration of 10 or 100 nmol EB per gram of body mass (earlier work showed the latter to be the minimum oral dose required to maximally masculinize female song nuclei) or an equimolar amount of OP daily from 5 through 11 days of age. Canola oil was used as a vehicle and control. Reproductive testing was done either in individual pair cages or in communal cages that permitted self-selection of mates, N = 10 pairs per group. Pairs consisted of EB-treated males and females, EB-treated males paired with canola-treated females, vice versa, and canola-treated males and females. Posthatch EB treatment produced sex-specific impairments in reproduction that, in some instances, were additive when both sexes were treated. Egg production was reduced and egg breakage was increased in 100 nmol/g EB-treated male and female pairs. The incidence of missing eggs was increased in 10 nmol/g EB-treated male and female pairs. Candled fertility was reduced in both groups containing 100 nmol/g EB-treated males. The number of hatched chicks was severely reduced in all EB-treated groups. No adverse effects of OP treatment were detected. These significant treatment effects (all P < 0.05) show that posthatch EB treatment profoundly disrupts the reproductive performance of zebra finches, suggesting that exposure to estrogens in the wild could impair the reproductive performance of wild populations.

Immunolocalization of progesterone and estrogen receptors in the sperm storage tubules of laying and diethylstilbestrol-injected immature hens

The goal of this study was to determine whether sperm storage tubules (SST) in the uterovaginal junction (UVJ) contain receptors for progesterone and estrogen (PR and ER) and whether estrogenic stimulation induces activation of these receptors in the SST. Frozen sections of UVJ obtained from immature chicks treated with or without diethylstilbestrol (DES), which is an estrogenic substance, and those from laying hens were immunostained for PR and ER. In laying hens, immunoreactions for PR were observed in the SST cells and on the surface epithelium of UVJ; the strongest reactions appeared in the SST cells. In contrast, ER immunoreactions were localized in the SST cells but not in the other cells. Immunoreactions for PR and ER were negligible in the UVJ of control immature birds that received only the oil vehicle. However, in the DES-treated birds, PR immunoprecipitates were localized in the surface epithelium and SST cells, and there were ER in the SST cells. These results suggest that the SST cells in the UVJ contain PR and ER, and estrogenic stimulation may play a significant role in inducing activation of these receptors.

Histomorphometric and progesterone receptor immunohistochemical analysis in the oviduct of newly hatched chicks treated with follicle-stimulating hormone during embryonic development

In this study we evaluated the histomorphology and ultrastructure of the oviduct of newly hatched chicks, as well as the immunohistochemical expression of progesterone receptor (PR) in this tissue after follicle-stimulating hormone (FSH) treatment on days 13, 15 and 17 of embryonic development. Results indicated a marked difference in the histology of the oviduct of newly hatched chicks treated with FSH. Magnum mucosa from these animals presented a pseudostratified epithelium with evaginations from the lumen into the epithelium and from the latter into the stroma beneath where tubular glands are formed. In contrast magnum mucosa from control animals presented columnar epithelium with no evaginations. In magnum epithelium FSH also induced the formation of cilia and microvilli projections into the lumen as well as an increase in the wall and lumen areas and in the density of nuclei per unitarea. PR immunoreactivity was only observed in the oviduct of FSH treated animals. PR was located in the nucleus of epithelial luminal cells, mucosal stromal cells and smooth muscle cells. These findings suggest that FSH induces an adequate hormonal milieu for the cytodifferentiation and PR gene expression in the chick oviduct.

Cell proliferation in the process of oviducal tissue remodeling during induced molting in hens

Tissue remodeling and calcium binding protein-D28K (CaBP-D28K) dynamics were examined in the oviduct relative to induced molting. The oviducal tissues of premolting, 7, 10, 13, and 16 d after cessation of laying, and postmolting hens were examined. Frequency of proliferating cells and immunoreactive CaBP-D28K molecules were identified by immunocytochemistry for proliferating cell nuclear antigen (PCNA) and Western blot for CaBP-D28K. The relative frequency of PCNA-positive cells in the mucosal epithelium of the magnum, isthmus, and shell gland was low in premolting and 7 d after the cessation of egg laying. In the magnum and isthmus it was markedly increased in 10 and 13 d after cessation, followed by a slight decrease at 16 d after cessation. The frequency in the shell gland was kept high 10, 13, and 16 d after cessation. The frequency of PCNA-positive cells in each segment was decreased when the birds resumed laying. In the stroma of magnum and isthmus where the tubular glands were located, the frequency of PCNA-positive cells was significantly increased 10 d after the cessation of egg laying relative to premolting and 7 d after cessation. In postmolting hens and in hens 16 d after cessation, the frequency was decreased to a same level to that of premolting hen. In the shell gland, the frequency of PCNA-positive cells was high at 10, 13, and 16 d, and diminished in postmolting hen. Single immunoprecipitate band for CaBP-D28K was observed in the shell gland of premolting, postmolting, and younger hens, whereas the density of bands was greater in postmolting hens and younger hens than in premolting hens. We suggest that the oviducal tissues are remodeled by replacing the old glandular cells with new ones that are derived from the mucosal epithelium and uninvoluted glandular cells. Such rejuvenation of shell gland tissue may lead the improvement of CaBP-D28K induction.

Turtle oviduct progesterone receptor: radioligand and immunocytochemical studies of changes during the seasonal cycle

In order to determine the regulation of the oviduct progesterone receptor inChrysemys picta, radioligand binding studies were performed to determine changes in the high and lower affinity binding sites during the seasonal cycle. Lower affinity sites were present in both cytosolic and nuclear fractions during the cycle and peaked during the peri-ovulatory/early luteal periods. The high affinity sites, present exclusively in the nuclear fraction, increased following the preovulatory peak in plasma estradiol, remained elevated during the early luteal phase following the post-ovulatory peak in progesterone, and declined to non-detectable levels just before egg-laying. DNA-cellulose affinity chromatography showed that both high and low affinity binding sites were integral to both progesterone receptor B and A isoforms. Western blot analysis confirmed the binding studies and showed that PR-B (115 kDa) was present in greatest amounts during the peri-ovulatory and luteal periods, whereas PR-A (88 kDa) increased during those periods and was present following egg-laying. Immunocytochemical analysis revealed increased progesterone receptor immunostaining from the winter to the peri-ovulatory period in the three major zones (luminal epithelium, submucosal glands and the myometrium) following the preovulatory peak in estradiol, a decrease in all three zones, especially the myometrium, in the late luteal period following the post-ovulatory peak in progesterone, and an increase again during fall recrudescence. Competition studies demonstrated that progesterone was the most effective competitor followed by pregnenolone, R5020 and deoxycorticosterone. RU 486 does not bind to the high affinity site, but binds quite well to the lower affinity site. This study suggests that progesterone receptor isoforms in the turtle oviduct may be under the regulation of changing estrogen/progesterone ratios during the cycle.

Effects of insulin-like growth factor-I, estrogen, glucocorticoid, and transferrin on the mRNA contents of ovalbumin and conalbumin in primary cultures of quail (Coturnix coturnix japonica) oviduct cells

The effects of estrogen, dexamethasone, insulin-like growth factor-I (IGF-I), and transferrin on the messenger RNA (mRNA) contents of ovalbumin and conalbumin in primary cultures of quail oviduct cells were investigated. In the absence of one of the above hormones or factors, a decrease in ovalbumin mRNA was prominent. In particular, removal of IGF-I and transferrin caused a significant effect. Studies using a combination of estrogen, dexamethasone, IGF-I and transferrin indicated that IGF-I cooperates with estrogen or dexamethasone and transferrin works with dexamethasone. Specifically, IGF-I enhanced ovalbumin synthesis or increased cellular ovalbumin mRNA content depending on its concentration in the medium in the presence of estrogen. However, the effects of estrogen, dexamethasone, IGF-I, and transferrin were not similarly observed with conalbumin mRNA. These results show that ovalbumin synthesis is controlled by estrogen or glucocorticoid with IGF-I or transferrin and that cellular ovalbumin mRNA content is also regulated by these hormones or transferrin. In contrast, conalbumin synthesis and cellular content of conalbumin mRNA are not affected by these hormones under the conditions of the present study.

Effects of estradiol and progesterone on the cytodifferentiation of epithelial cells in the oviduct of the newborn golden hamster

The effects of estradiol and progesterone on the cytodifferentiation of epithelial cells in the oviduct of the newborn golden hamster were investigated by electron microscopy. Consecutive daily injections of estradiol-17 beta (E2) induced various ultrastructural changes in undifferentiated epithelial cells of the neonatal oviduct. Ciliogenesis, formation of some ciliary buds, and ciliation were frequently observed in the oviductal epithelial cells on days 1-4 of consecutive treatments with E2. On days 2 and 3, the remaining cells contained well-developed Golgi apparatus and rough endoplasmic reticulum. Thereafter, a few secretory granules were observed in the cytoplasm of these cells, indicative of differentiation into secretory cells. Occasionally, secretory cells undergoing ciliogenesis or mitosis were found in the epithelium. On day 9, many fully mature ciliated and secretory cells were observed. Quantitative studies clearly showed that E2 induced the differentiation of both ciliated and secretory cells. By contrast, consecutive daily injections of progesterone significantly stimulated the appearance of ciliogenic and ciliated cells but not that of secretory cells. These results indicate that the induction of differentiation of secretory cells is a specific effect of estrogen, whereas the differentiation of ciliated cells may be closely related to effect of progesterone as well as of estrogen. It is suggested that hormonal effects on differentiation differ between ciliated and secretory cells in the oviductal epithelium of the newborn golden hamster.

Comparison of sex steroid hormone-dependent induction of chick oviduct delta-aminolaevulinic acid dehydratase during primary and secondary stimulation

1. A comparative study on primary and secondary stimulation of oviduct delta-aminolaevulinic acid dehydratase (ALAD) (EC 4.2.1.24) was carried out with oestradiol-17 beta and/or testosterone administration in immature female chickens during 15-day-primary stimulation, 20-day-withdrawal and 15-day-secondary stimulation periods. 2. Compared with primary stimulation in oestrogenized birds, synthesis and degradation rates of oviduct ALAD molecule during secondary stimulation increased 3.4- and 1.8-fold respectively, resulting in a rapid induction of the enzyme. 3. Specific activity of oviduct ALAD in oestradiol-plus-testosterone treated birds became significantly higher than that of oestradiol alone during secondary stimulation, whereas no significant changes were observed during primary stimulation.

The effects of hormonal and other stimuli on cell-surface Ro/SSA antigen expression by human keratinocytes in vitro: their possible role in the induction of cutaneous lupus lesions

Ultraviolet B light (UVB) has previously been shown to induce the expression of the extractable nuclear antigens (e.g. Ro/SSA) on the surfaces of human keratinocytes in vitro. This study assessed whether injurious, metabolic, inflammatory, immunological or hormonal stimuli would also induce this expression or modulate that produced by UVB. No stimulus initiated expression alone, but 17-beta oestradiol doubled that found in response to UVB. These findings confirm the potential role of UVB in the initiation and potentiation of cutaneous lupus lesions and may help to explain the female preponderance of the disease.

The effect of dihydrotestosterone on the estrogen-induced cytodifferentiation of the chick oviduct

The androgenic effects on the estrogen-induced cytodifferentiation of the chick oviduct epithelium were investigated. Dihydrotestosterone was shown to have an effect on the organization of stromal cells. Since these cells contained androgen receptor (AR), it is reasonable to assume an involvement of androgens in the differentiation and functioning of these cells through a direct action. Immunohistochemical analysis revealed a wide distribution of AR. AR was shown to be expressed in both the endothelial and smooth muscle cells of blood vessels. In the immature oviduct AR was located in the epithelial, mesenchymal and mesothelial cells. In the differentiating oviduct, whether induced by exogenous estrogen or normally by endogenous hormones, AR was also expressed by the tubular gland cells. Dihydrotestosterone alone had no effect on the morphology of the immature oviduct, suggesting the involvement of the determinants of differentiation in the action of androgen together with estrogen.

The fabrication and collagenous substructure of the eggshell membrane in the isthmus of the hen oviduct

The eggshell of the chicken consists of a bi-layered shell membrane overlaid with a thick, calcified shell matrix. The shell membranes and matrix are deposited onto the egg as it passes through the oviduct. To assess the temporal and spatial aspects of the fabrication of type X collagen within the eggshell extracellular matrix, the immunohistochemical localization of type X collagen was studied in three regions of the hen oviduct (magnum, isthmus and uterus), in the membranes of uncalcified eggshells obtained from the oviduct prior to mineral deposition and in eggshell membrane and calcified eggshell matrix. Additionally, immunohistochemical localization of type I and III collagens was done in order to determine possible co-localization of collagen types or to define tissue compartments. None of the collagen epitopes assayed was found in the shell matrix. Type X collagen epitope was immunohistochemically localized only to the epithelial cell layer lining the isthmus region of the oviduct and in the shell membranes of both uncalcified and calcified eggshells. Antitype III collagen monoclonal antibody delineated the inter-tubular gland connective tissue of the oviduct and was negative in the shell layers under conditions which gave strong connective tissue reactivity. Type I collagen epitope was exposed after pepsin treatment of the tissue and co-localizes with the distribution of type III collagen. Type I collagen co-localized with type X collagen in the shell membranes of uncalcified shells. The type I collagen epitope was reactive in the shell membrane of the uncalcified shells, but could only be detected in calcified shells following pepsin digestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Progesterone downregulates progesterone receptor, but not estrogen receptor, in the estrogen-primed oviduct of a turtle (Trachemys scripta)

Progesterone downregulates nuclear progesterone receptor (Rp) and estrogen receptor (Re) in the estrogen-primed mammalian uterus and chick oviduct. We sought to determine if this downregulation mechanism is operative in the turtle oviduct. Female turtles were primed for 4 days with 17-beta-estradiol, after which progesterone (5 mg) was administered by injection every 24 h. Re and Rp levels in progesterone-treated and control turtle oviducts were measured by [3H]steroid-binding assays (pyridoxal 5' phosphate method) at 12, 24, 48 and 72 hr after initial progesterone treatment. Serum progesterone levels of progesterone-treated turtles increased only slightly from 0 hr (0.3 ng/ml) to 12 hr (0.6 ng/ml) after progesterone administration, increased considerably by 24 hr (5.3 ng/ml), and remained elevated (6-8 ng/ml) through 72 hr. Cytosol and nuclear Rp levels of estrogen-primed turtle oviducts showed distinct seasonal variation, with Rp levels higher in spring and summer months than in winter months. There was no seasonal variation in Re levels. Both cytosol and nuclear Rp responded to progesterone treatment. Cytosol Rp levels of progesterone-treated oviducts were significantly reduced below control levels by 12 hr after progesterone administration and remained low through 72 hr. Nuclear Rp levels of progesterone-treated oviducts showed no change at 12 hr, increased at 24 hr and then dropped at 48 and 72 hr. However, progesterone did not downregulate Re in the turtle oviduct.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in ovalbumin and protein synthesis in vivo in the magnum of laying hens during the egg formation cycle

1. The present study was carried out to investigate whether or not the rate of synthesis of total protein in various oviducal segments and ovalbumin, a major egg white protein, in the magnum fluctuated during the egg formation cycle in laying hens. 2. Synthesis of total protein and ovalbumin was measured in vivo by the incorporation of [15N]methionine after a primed continuous infusion of tracer for 3 hr. 3. Protein and ovalbumin contents in the magnum and the entire oviduct decreased sharply when an ovum moved down from the magnum to the isthmus, probably due to the secretion of egg white proteins. 4. In contrast, total protein and ovalbumin synthesis in the magnum was significantly higher when an ovum was in there than when it was in any other segments. Fluctuations of ovalbumin synthesis and total protein synthesis in the magnum were roughly parallel to those of total protein synthesis in the entire oviduct. 5. It was concluded, therefore, that the changes seen in total protein synthesis in the whole oviduct during the egg formation cycle were mainly attributable to those in magnum protein synthesis, of which a significant portion was accounted for by the synthesis of ovalbumin.

Chick oviduct differentiation. The effect of estrogen and progesterone on the expression of progesterone receptor

Progesterone receptor (PR) is a marker of estrogen action. Its cellular appearance during estrogen (20 mg/kg i.m.)-induced differentiation of the immature chick oviduct was therefore studied by immunohistochemistry. PR was located in the epithelial, mesothelial, submucosal stromal and smooth muscle cells. Progesterone (20 mg/kg i.m.) caused an obvious decrease in PR immunoreactivity without inducing synthesis of progesterone-dependent avidin. Thus mere receptor occupation by ligand is not sufficient for this induction. This paper reports that the expression of PR in the mucosal stromal cell differs from that in other cell types. In the mucosal stromal cell PR was inducible, i.e., not shown without the action of estrogen. The formation of tubular glands did not commence before mucosal stromal cells expressed PR. It would seem that the mucosal stromal cells have a crucial role in mediating epithelial differentiation. The onset of differentiation was preceded by vascularization and invasion of mononuclear cells in the submucosa. It was conspicuous that the smooth muscle cells of arteries also contained PR.

Comparison of delta-aminolaevulinic acid dehydratase activity in chick liver during sex steroid hormone dependent primary and secondary stimulation

1. Comparative study on primary and secondary stimulation of hepatic delta-aminolaevulinic acid dehydratase (ALAD) (EC 4.2.1.24) was carried out after oestradiol-17 beta and/or testosterone administration in immature female chicken. 2. When 2 mg/day oestradiol was administered to birds for 15 days successively, hepatic total ALAD activity increased to 170% by day 15 of primary stimulation, whereas a more rapid increased rate was observed within day 3 of secondary stimulation and thereafter the hepatic ALAD activity maintained the same high level from day 3 to day 15. 3. Testosterone (2 mg/day) alone decreased hepatic total ALAD activity during both primary and secondary stimulation. 4. When testosterone (0.25-10 mg/day) was injected into birds in combination with 2 mg oestradiol for 15 days during primary and secondary stimulation, only an antagonistic effect of testosterone on oestradiol-stimulated total ALAD activity in liver was observed independently of the testosterone amount administered. However, the extent of suppression of hepatic ALAD activity by testosterone during primary stimulation was markedly different from that of secondary stimulation.

Progesterone down-regulation of nuclear estrogen receptor: a fundamental mechanism in birds and mammals

Progesterone is known to selectively down-regulate nuclear estrogen receptor (Re) in the mammalian uterus, and this process is functionally related to embryo retention. It is unclear if this mechanism is operative in the chick oviduct, where egg retention does not occur. We investigated the regulation of Re by progesterone in a mammalian model (proestrous hamster uterus) and an avian model (DES-primed chick oviduct), under the same assay conditions, in an effort to compare progesterone action in viviparous and oviparous species. Nuclear and cytosol estrogen receptor were measured with an assay employing pyridoxal 5'-phosphate (PLP). The PLP assay has the advantage of allowing exchange at low temperature, which results in improved receptor recovery, especially from the nuclear fraction. Parallel studies were done under two different hormonal settings, estrogen primed and estrogen + progesterone primed. Experiments were: (1) response of Re to acute progesterone treatment (5 mg progesterone, 4 hr) in estrogen-primed preparation, (2) time course of the Re down-regulation response (4, 8, and 12 hr after progesterone treatment), and (3) recovery of Re after progesterone withdrawal in estrogen + progesterone-primed preparation. Chick oviduct contained little cytosol Re (0.96 +/- 0.32 pmol/g tissue) compared to hamster uterus (4.27 +/- 0.15 pmol/g tissue), and progesterone treatment had no effect on cytosol Re levels in either species. Nuclear Re levels were similar for chick oviduct (2.68 +/- 0.14 pmol/g tissue) and hamster uterus (2.64 +/- 0.14 pmol/g tissue). Progesterone treatment reduced nuclear Re levels in both the hamster uterus and chick oviduct to about 50% of control levels. In the chick oviduct, down-regulation was transient, as evidenced by complete recovery of nuclear Re to control levels by 12 hr after progesterone administration. In the estrogen + progesterone-primed chick oviduct, nuclear Re increased within 6 hr after progesterone withdrawal and approached maximal levels by 12 hr. These data indicate that progesterone rapidly and selectively down-regulates the nuclear form of Re in the chick oviduct as in the hamster uterus. Thus, the regulation of Re by progesterone appears to be similar in the mammalian uterus and the chick oviduct, despite the basic differences in reproductive strategy between birds and mammals.(ABSTRACT TRUNCATED AT 400 WORDS)

Concentration of steroid sex hormones in the plasma of hens in relation to oviduct tumours

1. The concentrations of 17 beta-oestradiol (E2) and progesterone (P) were determined in the plasma of layer breeder hens at the end of their first laying season, in relation to neoplasms of the oviduct, including magnum tumours and leiomyomas. 2. The plasma concentration of E2 was higher in tumorous than in non-tumorous hens indicating it may be involved in the development of oviduct tumours. 3. The plasma concentrations of P in tumorous and non-tumorous hens were not significantly different, suggesting no active role of P in the aetiology of the tumours. 4. The E2: P ratio was higher in tumorous than in non-tumorous hens. This ratio could be of value in predicting hens at risk of developing oviduct tumours.

Incorporation of mevalonate into dolichol and other isoprenoids during estrogen-induced chick oviduct differentiation

Incorporation of [14C]mevalonate into dolichol and other isoprenoid compounds by chick oviduct explants has been studied. A reliable assay of dolichol biosynthesis employing several chromatographic procedures, including two-dimentional TLC, was developed. Incorporation of [14C]mevalonate into dolichol by oviduct explants was linear for at least 6 h. The effect of estrogen-induced differentiation was studied by incubation of explants obtained from chicks treated for various periods of time with diethylstilbestrol. Mevalonate incorporation into dolichol, when expressed as cpm per g of tissue, was not affected by estrogen treatment, but since the oviduct increased about 100-fold in mass during differentiation, each oviduct synthesizes about 100-fold more dolichol. In most tissues, the major product of mevalonate incorporation is cholesterol. However, although approx. 90% of the non-saponifiable 14C-labeled compounds were in the so-called 'cholesterol fraction', oviduct explants from estrogenized chicks synthesized little, if any, cholesterol. A number of cholesterol biosynthetic intermediates were observed, with compounds comigrating with squalene and lanosterol accounting for about 50% of the total. Since the estrogenized chick has serum cholesterol levels in the range of 800-900 mg/dl, these results suggest that oviduct has secondary control points which allow it to inhibit cholesterol synthesis when mevalonate is used as the precursor. In support of this hypothesis is the observation that explants from untreated chicks can incorporate mevalonate into cholesterol.

Down regulation of c-myc, c-fos and erb-B during estrogen induced proliferation of the chick oviduct

Oncogenes c-myc, H-ras, c-fos and erb-B were constitutively expressed in immature chick oviduct withdrawn from estrogen administration for 2.5 weeks after 10 d of primary estrogen stimulation. Following secondary estrogen stimulation of the withdrawn chicks, synthesis of egg white proteins is rapidly induced and remaining non-functioning tubular gland cells are stimulated to proliferate with a doubling time of 24 h. During first 12 h of secondary estrogen stimulation, H-ras mRNA levels doubled and did not increase further at 24 h and 48 h. The steady state levels of c-myc, erb-B and c-fos mRNA decreased 24 h following secondary estrogen stimulation. The levels of these oncogene RNAs in oviduct were similar at 48 h following secondary estrogen stimulation to those from immature chicks administered 10 d of primary estrogen stimulation. Thus elevated expression of c-myc and c-fos mRNA does not appear to be necessary components for sustained estrogen induced cell proliferation in the chick oviduct.

Comparison of sex hormone dependent induction of delta-aminolevulinic acid dehydratase in chick liver and oviduct

1. Comparative study on induction of hepatic and oviduct delta-aminolevulinic acid dehydratase (EC 4.2.1.24, ALAD) was performed following estradiol-17 beta and/or testosterone administration in immature female chicken (Gallus domesticus). 2. The lowest amount of estradiol for maximal induction of hepatic and oviduct ALAD activity was 2 mg/day/bird. 3. When estradiol of 2 mg/day/bird was administered for 15 days successively, induction extent of oviduct ALAD molecule was markedly larger and became approximately 144-fold in comparison with that of liver. Testosterone (2 mg/day/bird) alone did not induce both hepatic and oviduct ALAD activity. 4. Synergistic and antagonistic effect of testosterone on estradiol-induced total ALAD activity in oviduct was dependent on testosterone amount administered, whereas testosterone antagonized the inductive effect of estradiol on liver ALAD activity, independently of its amount.

Expression of the avian c-erb B (EGF receptor) protooncogene during estrogen-promoted oviduct growth

Expression of cellular erb B protooncogene messenger RNAs has been analyzed in the oviducts of immature chicks during estrogen-promoted growth. Hybridization of oviduct total cellular RNA with viral-derived erb B oncogene probes demonstrated significant expression of c-erb B mRNA in oviduct cells of untreated chicks. Daily administration of estrogen (diethylstilbestrol) to chicks results in marked oviduct growth but did not appreciably affect expression levels of c-erb B messenger RNA in oviducts after 2, 4 or 6 days of treatment. Withdrawal of chicks from estrogen treatment resulted in termination of oviduct growth. However, c-erb B messenger RNAs were detectable in the nonproliferative tissue at 5 days after hormone withdrawal. Readministration of diethylstilbestrol, progesterone or diethylstilbestrol plus progesterone to hormone-withdrawn birds (secondary stimulation) also did not affect c-erb B messenger RNA levels in the oviduct. These results demonstrate significant expression of the cellular erb B (epidermal growth factor receptor) gene in the avian oviduct. However, EGF receptor messenger RNA synthesis is not modulated in the oviduct by steroid hormones.

Estrogen-dependent DNA synthesis in cultures of Xenopus liver parenchymal cells

We have recently shown that extensive proliferation of liver parenchymal cells takes place in adult male Xenopus frogs in response to estradiol-17 beta, which also induces synthesis and secretion of vitellogenin, the precursor of yolk proteins. We demonstrate here that liver parenchymal cells from adult male animals can be maintained for several weeks in a defined tissue culture medium containing added insulin, dexamethasone, and triiodothyronine. Under these conditions the cells do not divide, but can synthesize DNA. Maximum DNA synthesis occurs in cells that have achieved monolayer morphology under low plating densities. Estradiol-17 beta causes a dose-dependent increase in the number of cells synthesizing DNA, as well as inducing synthesis of vitellogenin. Estrogen-dependent, but not background, DNA synthesis is inhibited by the antiestrogen tamoxifen. These results imply that estradiol-17 beta acts directly on liver cells to initiate DNA replication, probably by interaction with a receptor protein and induction of specific gene transcription.

Hormonal induction of riboflavin carrier protein in the chicken oviduct and liver: a comparison of kinetics and modulation

Estrogen (E) induction of riboflavin carrier protein (RCP) in the chicken oviduct and liver was investigated to compare and contrast the kinetics, hormonal specificity and modulation of its elaboration in the 2 steroid-responsive tissues. During primary stimulation, continued daily E administration to immature female chicks elicited, after an initial lag, rapid growth and RCP content of the overduct; neither progesterone (P) nor testosterone (T) could substitute for E in this respect. Furthermore, P given along with E curtailed tissue growth and its RCP content, whereas E + T had a synergistic effect on tissue growth only. During secondary stimulation, E administration steeply enhanced both tissue weight and RCP content without any lag. Interestingly, P (but not T) could substitute for E in augmenting magnum RCP concentration to a comparable extent while a concomitant effect on tissue growth was less marked. In contrast, hepatic induction of RCP was absolutely E-specific during both primary and secondary stimulations. Secondary stimulation with either E or P of E-primed birds enhanced the rates of RCP synthesis in the oviduct relative to that of total protein, whereas in the liver only E was effective in this regard. The absolute rate of E-induced RCP synthesis in both the steroid-stimulated tissues was significantly higher than that of general protein elaboration.

Evidence for a dissimilarity of chicken oviducts differentiated by diethylstilboestrol and oestradiol-17 beta: a study of progesterone-induced egg-white protein (avidin) synthesis

The growth and differentiation of chick oviducts were caused by daily diethylstilboestrol (DES) or oestradiol-17 beta (E2) injections, and the effects of these oestrogens on the progesterone-induced production of a biotin-binding egg-white protein (avidin) were studied. In the DES primed oviducts, but not in the E2 primed ones, both DES and E2 administered with progesterone potentiated avidin production 2 to 3-fold, even after 10-day oestrogen withdrawal. The results suggest that DES and E2 prime the avian reproductive target tissue differently.

Localization of the lipid intermediate pathway of protein glycosylation in oviduct cell types

Oviduct tissue slices were incubated with [3H]-leucine or [3H]-mannose in the presence and absence of tunicamycin, a specific inhibitor of lipid-mediated protein glycosylation. Conditions were established where tunicamycin had maximal effect on [3H]-mannose incorporation (greater than 90% inhibition) but a minimal effect on [3H]-leucine incorporation (less than 10% inhibition) into total TCA-insoluble products. Analysis of incubated tissues by SDS-polyacrylamide gel electrophoresis revealed that in the absence of tunicamycin, [3H]-mannose was incorporated into only a few proteins, of which ovalbumin represented the major radiolabeled component. Tunicamycin markedly reduced the incorporation of [3H]-mannose into ovalbumin and other oviduct glycoproteins. In contrast, analysis by SDS-polyacrylamide gel electrophoresis showed that [3H]-leucine was incorporated into a variety of proteins in the absence of tunicamycin. The radioactivity profile of some of these proteins was shifted toward lower Mr when oviduct slices were incubated in the presence of tunicamycin, with only a minimal decrease in protein labeling. Light microscopic autoradiograms of tissue incubated with [3H]-leucine in either the presence or absence of tunicamycin exhibited extensive labeling of tubular gland and epithelial cells. In the absence of tunicamycin, these cell types also become markedly labeled with [3H]-mannose; however, incorporation of label in both cell types was substantially reduced in the presence of tunicamycin. Qualitatively, labeling of tubular gland cells appeared greater than that of epithelial cells, largely due to the concentration of silver grains over the dense population of secretory vesicles in the tubular gland cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Zinc secretion in the oviduct of the coturnix quail

The oviduct from laying quail were used to investigate mechanisms of trace mineral secretion and the possible role of metallothionein in this process. Secretion of zinc occurred maximally at pH 5.4, which is close to the normal pH of the oviduct. Secretion occurred to a much greater extent in the isthmus and shell gland than in the magnum, the major protein-secretory section of the oviduct. Intraperitoneal administration of cadmium resulted in a marked reduction in Zn secretion from the oviduct of laying quail. This effect could not be correlated with metallothionein since metallothionein could not be detected in any section of the oviduct in control or Cd-induced quail. Small-molecular-weight metal-binding ligands were present in the isthmus and shell gland, which may play a role in trace mineral mobilization. Histological evaluation by light and elelctron microscopy show that Zn is transported from the smooth muscle cells through the connective tissue matrix in the extracellular space to the epithelial goblet cells. Presumably, Zn and other trace minerals are secreted from the secretory goblet cells into the egg.

Chick oviduct glucocorticosteroid receptor. Specific binding of the synthetic steroid RU 486 and immunological studies with antibodies to chick oviduct progesterone receptor

The glucocorticosteroid receptor (GR) has been studied in oviduct cytosol prepared from estrogen-primed, 4-week-withdrawn chicken. The equilibrium dissociation constant was 6 nM for dexamethasone, and 18 300 receptor sites/cell were measured assuming that all cells contain identical concentrations of GR. Dexamethasone, used in most studies investigating glucocorticosteroid action, was found not to be the best GR ligand. The affinities of several natural and synthetic glucocorticosteroids for GR increased in the following order: cortisol less than deoxycorticosterone less than dexamethasone less than corticosterone less than triamcinolone acetonide. The synthetic steroid RU 486 was the most specific ligand of GR (its affinity was approximately equal to 10-fold higher than that of triamcinolone acetonide), while it did not bind either to plasma transcortin (which binds dexamethasone nor, surprisingly, to progesterone receptor (PR), contrary to what occurs in mammalian species. The molybdate-stabilized, 8-S form of GR was prepared from withdrawn chick oviduct, whole chick embryo or cultured chick embryo fibroblasts (which do not contain PR), and was labeled with either [3H]dexamethasone or [3H]RU 486. The sedimentation coefficient of radioactive ligand--8-S GR complexes was shifted towards heavier forms after incubation with polyclonal (IgG-G3) or monoclonal (BF4) antibodies generated against the molybdate-stabilized, 8-S form of the chick oviduct PR. Since neither IgG-G3 nor BF4 interacted with the steroid binding 4-S form of GR, it is suggested that these antibodies recognized a non-steroid binding protein common to molybdate-stabilized, 8-S forms of GR and PR.