Gonadotropine glycoproteique maturante et oestradiol-17β pendant le cycle reproducteur chez la truite fario (Salmo trutta) femelle

Maturational glycoprotéique gonadotropin and estradiol-17β during the reproductive cycle of the female brown trout (Salmo trutta). Female brown trout were sacrificed every month or twice a month during the reproductive season. Plasma gonadotropin (GtH) and estradiol-17β (E₂-17β) were measured using radioimmunological techniques, in relation with the state of gametogenesis. From ovulation to July egg's diameters remained less than 1 mm, and ovogenesis was characterized from the histological appearance of three types of vitellus: glycoproteique (type I), lipidique (type II), lipidoprotéique (type III), and the immunological plasma detection of the vitellogenin. During this period GtH levels remained lower than 1 ng/ml except in March, when they increased around 5 ng/ml, both with pituitary GtH and plasma E₂ 17β. This rise occurred just before the appearance of the type III vitellus within the oocyte, and might correspond to a critical phase of the reproductive cycle during which vitellogenin could not be detected in 70% of the animals. During rapid growth of the oocyte from 1 to 5 mm, mean GtH levels increased from 0.75 to 2.5 ng/ml when those of the E₂-17β increased more rapidly but began to drop before the end of vitellogenesis. Maturation and ovulation were accompanied by a rise of the GtH level, in correlation with the lower levels of E₂-17β measured during the cycle, GtH remained high even after ovulation, and more in fish which had kept their eggs within the body cavity. Correlation among GtH, E₂-17β, and the diameters of eggs had been calculated. There was a positive correlation among GtH, E₂-17β levels, and the diameters of eggs during exogenous vitellogenesis, and a negative between GtH and E₂-17β at the end of the reproductive cycle. These results were discussed, in relation to the existence of a pulsatile mode of GtH secretion.     

Transient administration of estradiol-17 beta establishes an autoregulatory loop permanently inducing estrogen receptor mRNA

A single transient dose of estradiol-17 beta is sufficient to elicit the permanent induction of hepatic estrogen receptor mRNA, which is induced 18-fold (from 0.13 to 2.4 molecules per cell) and then remains fully induced for at least 125 days. In primary liver cultures, extremely low concentrations of estradiol-17 beta, which are below the Kd of the Xenopus laevis estrogen receptor, maintain persistent induction of estrogen receptor mRNA but not of estrogen-inducible vitellogenin mRNA. These data and the ability of the antiestrogen, hydroxytamoxifen, to reverse persistent induction of estrogen receptor mRNA, support a model in which transient doses of estradiol-17 beta induce the estrogen receptor and thereby establish an autoregulatory loop. The low levels of estradiol-17 beta normally circulating in male X. laevis and the elevated level of receptor provide sufficient hormone-receptor complex to permanently maintain the induced level of expression of the estrogen receptor gene. The permanent induction of the estrogen receptor may be the regulatory switch that results in the persistent expression of a recently identified class of proteins that exhibit long-term responses to estrogen.     

Molecular identification of estrogen receptors (ERα and ERβ) and their differential expression during VTG synthesis in the liver of lizard Podarcis sicula

In non-mammalian vertebrates yolk deposition in the oocytes is a hormone-dependent, gender-specific process. Produced by the ovary under gonadotropin stimulation, Estradiol 17-β (E₂) plays a key role in the liver synthesis of vitellogenin (VTG) which in turn is taken up by vitellogenic oocytes in the ovary. In many species a negative role in liver synthesis of VTG in females is also played by progesterone. Experimental administration of E₂ induces the expression of the VTG silent gene also in the liver of males of all the species studied. However, the role of the two isoforms of estrogen receptors, ERα and β, in this process is still unclear.In order to elucidate what kind of ER is involved in the liver synthesis of VTG in the lizard Podarcis sicula, we obtained by means of RT-PCR two fragments of 430 bp and 130 bp from total ovarian mRNA, encoding respectively for ERα and ERβ. Expression analysis of these two specific isoforms of ERs in the liver showed that in non-breeding females, and in wildlife untreated males only ERβ is expressed. In breeding vitellogenic females and in E₂-treated males both α and β receptors are expressed. Furthermore, in females experimentally treated with progesterone during the breeding period, expression of ERα disappears. Conversely, treatment of females with E₂ in the non-breeding period induces expression of ERα. Immunohistochemical analysis and Western blotting showed that the presence of irVTG in liver and plasma is always parallel to hepatic expression of ERα in all the different experimental conditions. Our data strongly suggest that expression of ERα may be necessary for VTG synthesis in Podarcis. The possible modulatory role of ERβ is also discussed.     

Differential expression of three estrogen receptor subtype mRNAs in gonads and liver from embryos to adults of the medaka, Oryzias latipes

In fish, estradiol-17β (E2) regulates various reproductive processes by acting through estrogen receptors (ERs). Here, we cloned three ER subtypes from medaka and examined their developmental expression in the gonads and liver of genetically females and males from embryos to adults. During embryogenesis, marked increases in the expression of ERβ2, but not either ERα or ERβ1, were found in genetically female embryos during sex differentiation. E2 treatment induced marked up-regulation of ERβ2 expression in genetically male embryos. In adult ovaries, ERα levels were high in follicles (granulosa cells) during oocyte growth. In the testis, ERβ1 expression exhibited a distinct peak at 10 days post hatching (dph). In the liver, very high levels of ERβ2 were found in both females and males throughout the sampling period with significantly higher levels in females during 30-50 dph. These findings suggest each action of E2 to be mediated by different types of ERs.     

Estradiol-17β modifies the induction of spermidine/spermine N1-acetyltransferase activity in the liver of lipopolysaccharide-treated mice

ABSTRACT— In an attempt to elucidate the effects of estrogen on polyamine metabolism in lipopolysaccharide (LPS)-treated mice, we assayed polyamine content and the activity of spermidine/spermine N¹-acetyltransferase (SAT) and ornithine decarboxylase (ODC) in some organs. LPS elevated N'-acetylspermidine levels in the liver and lung and putrescine levels in the liver, lung and spleen. LPS increased the activity of ODC at 6 h and that of SAT at 12 h in the liver. When estradiol-17β was simultaneously administered with LPS, the maximum increase in hepatic N¹-acetylspermidine levels was found 6 h earlier than in the LPS control. Likewise, the peak of the hepatic SAT activity after LPS-treatment was observed 6 h earlier in the estradiol-17β-treated mice than in the LPS control. No such effect of estradiol-17β was found in the lung and spleen. The LPS-induced ODC activity was not affected by estradiol-17β in the liver, lung or spleen. Estrone and 16β-ethylestradiol (an anti-estrogen) were also effective in enhancing the LPS-induced elevation of N¹-acetyl-spermidine and putrescine in the liver, while both diethylstilbestrol, which has a potent estrogenic activity without steroid structure and estradiol-17α (a non-estrogenic isomer of estradiol-17β) were without effect. Tamoxifen (an estrogen receptor antagonist) did not suppress the estrogen-induced increase in hepatic N¹-acetylspermidine levels.     

Effect of exogenous estradiol-17β on plasma vitellogenin levels in male and female Chrysemys and its modulation by testosterone and progesterone

Injection of estradiol-17β into the freshwater turtle, Chrysemys picta induced hormone-specific and dose-dependent vitellogenic responses in both sexes. However, both the time course of induction and the magnitude of the responses showed marked sexual differences. No vitellogenin was detected in untreated males. Following a single injection of estradiol-17β (100 μg/100 g body wt) vitellogenin was first detected in the plasma 8 hr postinjection. Maximal levels (3.1 ± 0.8 mg/ml, n = 5) were obtained by Day 6. Multiple injections of estradiol-17β into males raised plasma vitellogenin levels to 10–20 mg/ml. The initial increases during the first 6 days post-hormone treatment were independent of the dose. Nonvitellogenic females have basal levels of 1–2 mg/ml vitellogenin in circulation. Female turles receiving equal amounts of estradiol-17β (100 μg/100 g body wt) as males demonstrated a response 10 times greater (32.6 ± 3.9 mg/ml, n = 5). Maximum levels were reached in 12–14 days. Multiple injections of the hormones brought plasma vitellogenin levels to concentrations attained during the natural vitellogenic season (40 mg/ml). When progesterone or testosterone were administered to male turtles in conjunction with estradiol-17β, both hormones inhibited the estrogen-induced vitellogenesis. The antagonistic effect of progesterone on estrogen was directly dose dependent; in contrast, the testosterone effect appeared to be inversely related to dose. Since both progesterone and testosterone concentrations reach high levels during the periovulatory phase of the gonadal cycle, it is suggested that these hormones may be of physiological significance in modulating vitellogenin level in the plasma.     

Effects of hydrostatic pressure on monoaminergic activity in the brain of a tropical wrasse, Halicoeres trimaculatus: possible implication for controlling tidal-related reproductive activity

Most wrasse species in tropical waters exhibit daily spawning synchrony with a preference for high tide. Fish perceive tidal rhythm cues through sensory organs and activate the brain-pituitary-gonadal endocrine axis for synchronous gonadal maturation, although how the tidal-related spawning cycle is controlled endogenously is not known. The purpose of this study was to examine whether hydrostatic pressure has an impact on brain monoamine levels and reproductive activities in the threespot wrasse Halichoeres trimaculatus. The contents of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) in the brain were measured using high-performance liquid chromatography and an electrochemical detection system. Exposing the fish to hydrostatic pressure occurring at a 3-m depth (~30 kPa) resulted in an increase in 5-HIAA/5-HT over 3h and a decrease in DOPAC/DA over 6h. No changes in gonadosomatic index or oocyte diameter were observed between the groups when female fish were reared at 0-m and 3-m depth for 3h. Hydrostatic pressure did not alter pituitary mRNA abundance of follicle stimulating hormone-β or luteinizing hormone-β. However, in vitro culture of ovaries from pressurized fish in the presence of human chorionic gonadotropin resulted in an increase in 17α,20β-dihydroxy-4-pregnen-3-one in the medium. These results suggest that hydrostatic pressure activates oocyte maturation through brain monoaminergic activity in this tropical wrasse species.     

Role of testosterone,estradiol-17β, and cortisol during vitellogenin synthesis in the catfish, Heteropneustes fossilis (Bloch)

Incubation of ovarian tissue obtained from vitellogenic catfish with labeled testosterone (T) resulted in the formation of labeled estrogens in the incubation medium. The amount of label recovered in the estrogen fraction increased with the duration of incubation as well as with T concentration in the medium, suggesting a precursor-product relationship between T and estrogens. Alkali-labile phosphorus (vitellogenin) was estimated in the plasma of hypophysectomized female catfish following administration of cortisol (10 or 20 μg/100 g body wt) or estradiol-17β (1 μg/100 g body wt) alone or in combination. Estradiol-17β administration significantly increased plasma vitellogenin levels; cortisol, which by itself did not bring about any increase in circulating vitellogenin levels, significantly potentiated the effect of estradiol-17β. Thus T, present in plasma of vitellogenic catfish, serves as a precursor for estrogen synthesis, and cortisol, whose levels in the plasma are high during ovarian recrudescence, enhances estrogen-induced vitellogenin synthesis in the catfish.     

In vivo estrogen induction of hepatic estrogen receptor mRNA and correlation with vitellogenin mRNA in rainbow trout

We have previously described the cloning, sequencing and in vitro expression of a full-length rainbow trout estrogen receptor cDNA (rtER cDNA). This full cDNA randomly labelled was used to study the estrogen induction of hepatic rtER mRNA in correlation with vitellogenin (Vg) mRNA in different physiological situations. In this paper, we show that in the liver two mRNA species are under hormonal control and their level increases about 8-fold after estrogen stimulation. These two mRNAs are expressed and induced in the liver as early as the hatching stage in correlation with the expression of Vg mRNA. A long-term analysis of rtER mRNA after estradiol (E2) injection shows a transient induction of the nuclear ER and its mRNA which recover to the basal level after 2 weeks. Nevertheless, a memory effect was observed on the expression of the Vg gene which does not appear to be directly related to the estrogen receptor level.     

Androgen-specific regulation of FSH signalling in the previtellogenic ovary and pituitary of the New Zealand shortfinned eel, Anguilla australis

The evidence for androgens having a pivotal role in the functioning of the female reproductive axis--such as initiating puberty or vitellogenesis--is mounting. However, the use of aromatizable androgens and the tissue-specific focus of most studies often make it unclear if androgenic effects throughout the axis proceed via androgen or estrogen signalling mechanisms. In this study, we assessed the effects of 11-ketotestosterone (11KT, a non-aromatizable androgen) on the pituitary and ovary of previtellogenic (PV) freshwater eels Anguilla australis, comparing them with eels naturally undergoing early vitellogenesis (EV). We found that 11KT treatment produces molecular and morpho-physiological phenotypes that were generally intermediate between PV and EV. Most notably, we demonstrated that 11KT induces effects on follicle-stimulating hormone (FSH) signalling in the pituitary and ovaries that are in opposition to each other. Thus, 11KT significantly reduced fshβ subunit expression in the pituitary. At the same time, 11KT dramatically increased mRNA levels of ovarian FSH receptor and plasma levels of estradiol-17β, very likely sensitizing the previtellogenic follicle to the FSH signal. Androgens therefore may be important in facilitating puberty in the eel.     

Modulation of ERα transcriptional activity by the orphan nuclear receptor ERRβ and evidence for differential effects of long- and short-form splice variants

Oestrogen receptor related proteins (ERRs) affect target gene expression without binding oestradiol. We investigated the functional activity of two splice variant isoforms of ERRβ (ERRβS [short], ERRβL [long]) expressed in human endometrium, where they are coexpressed with the oestrogen receptor alpha (ERα). Over-expression of ERRβL enhanced ERα-dependent ligand-induced activation of an ERE-luciferase reporter construct, altered the induction of c-myc mRNA and increased proliferation of Ishikawa cells whereas ERRβS was found to reduce these endpoints.     

Temporal expression of hepatic estrogen receptor 1, vitellogenin1 and vitellogenin2 in European silver eels

Because European silver eels have never been caught during or after their 6000-km reproductive migration to the Sargasso Sea, all existing knowledge on their sexual maturation comes from hormonal stimulation. Silver eels that start their oceanic migration are still immature with pre-vitellogenic oocytes. Hence we assumed that vitellogenesis should start with the expression of the estrogen receptor in the liver before the circulating 17β-estradiol (E2) can have any effect. In this study we followed the hepatic vitellogenesis upon 4 weekly injections with carp pituitary extracts (CPE). New molecular primers for the expression of the estrogen receptor 1 (esr1), vitellogenin1 (vtg1) and vitellogenin2 (vtg2) in the liver were developed. Sequences of vtg2 and esr1 were not previously described in Anguilla anguilla. All eels showed weekly increase of the eye size and pectoral fin length, which are signs of early maturation. The same occurred with the gonadosomatic index, the oocyte stage and diameter, and number of deposited fat droplets. Early vitellogenesis appeared as a 3-step process (1) E2-levels and esr1 expression were significantly increased already after one injection, (2) vtg1 and vtg2 expression were significantly increased after one and two injections, respectively, and (3) vtg1 and vtg2 expression increased further after three and four injections. Then also plasma calcium (corresponds with plasma vitellogenin) increased and yolk globuli appeared in the oocytes. These results show that esr1 is the first of the three genes examined that is expressed during the onset of hepatic vitellogenesis. Furthermore, ovarian vitellogenesis (appearance of yolk globuli in oocytes) occurs 1-2 weeks later than the onset of hepatic vitellogenesis.     

Effect of exogenous estradiol-17 beta on vitellogenic oocyte growth in ovaries of the toad Bufo bufo bufo (L.) during the postspawning period

The effects of injecting different doses of estradiol-17β for 3 or 7 weeks on ovarian function have been studied in toads during the postspawning period in an attempt to evaluate the possible role played by estrogen in the mechanisms that control the number of previtellogenic oocytes recruited to the second growth phase and their growth rate. It was found that intramuscular injections of peanut oil, which was used to dissolve estradiol-17β, retarded growth of the oocytes, but did not significantly reduce the recruitment of oocytes to the second growth phase. Injection of the physiologically active dose of 1 μg of estradiol-17β three times a week had no clear effects on ovarian development. Only large doses of estradiol-17β, 5 μg or more, reduced the number and size of second growth phase oocytes and caused atresia among the vitellogenic oocytes. The results are discussed and it is concluded that secretion of estradiol-17β, or other estrogens, from the ovary does not seem to play an essential role in the mechanisms that control gonadotropin secretion during the period of vitellogenic growth in the toad ovary.     

Relationship between expression of glucocorticoid receptor isoforms and glucocorticoid resistance in immune thrombocytopenia

Background: Glucocorticoids (GCs) play an important role in the treatment of several hematological malignancies, such as immune thrombocytopenia (ITP). The glucocorticoid receptor (GR) mediates the effects of GCs. Five isoforms of GR mRNA were described: GRα, GRβ, GRγ, GRP, and GRA. GR levels are regulated by alternative splicing of GR mRNA. Several studies demonstrated that a lower GR expression was associated with poor GC response.

Purpose: This study investigated the expression of GR isoforms and the relationship between GC resistance in ITP.

Methods: This study determined GRα/β/γ/P mRNA and GRα/β protein expression levels using SYBR Green Real-time PCR and Western blot, respectively, in 49 newly diagnosed ITP patients and 31 controls.

Results: The expression of GR isoform mRNA in ITP and controls showed the following trend: GRα?>?GRP?>?GRγ?>?GRβ. The expression of GRα, β mRNA and the total frequency of the four GR isoforms in ITP was significantly higher than in controls (P?<?0.05). The expression of GRα mRNA and protein in the GC-resistant group was significantly lower than that in the GC-sensitive group and controls (P?<?0.05). GRβ could not be detected at the protein level in our experimental conditions.

Conclusion: GRα and GRP were the main GR isoforms responsible for the effects of GC, and GRα and GRP exhibited synergistic effects. The down-regulation of GRα levels may play an important role in GC resistance in ITP. The effects of GCs in ITP were not associated with changes in GRβ and GRγ.     

Changes in GnRH I, bradykinin and their receptors and GnIH in the ovary of Calotes versicolor during reproductive cycle

The aim of this study was to investigate changes in the abundance of gonadotrophin releasing hormone I (GnRH I) and GnRH I receptor in the ovary of Calotes versicolor during the reproductive cycle and correlate them with the changes in gonadotrophin inhibitory hormone (GnIH), bradykinin and bradykinin B(2) receptor in order to understand their interaction during ovarian cycle. GnRH I, bradykinin and their receptors and GnIH, were localized immunohistochemically in the ovary. Relative intensity of these peptides was estimated from the contralateral ovary using slot/Western blot followed by densitometry. The immunostaining of GnRH I, bradykinin and their receptors and GnIH were localized in the granulosa cells of previtellogenic follicles and stroma cells, whereas in the peripheral part of the cytoplasm in oocytes of vitellogenic and ovulatory follicles. The GnRH I immunostaining was relatively higher in inactive phase, but was low during active preovulatory phase suggesting inverse correlation with circulating estradiol level. The study showed a positive correlation between the expression pattern of GnRH I and GnIH, but showed a negative correlation between GnIH with GnRH I receptor in the ovary. This study further suggests a possibility for bradykinin regulating GnRH I synthesis in the ovary. An increase in the immunostaining of both GnRH I and GnIH in the oocyte prior to ovulation suggests their involvement in the oocyte maturation. It is thus concluded that the ovary of C. versicolor possesses GnRH I-GnIH-bradykinin system and interaction between these neuropeptides may be involved in the regulation of follicular development and oocyte maturation.     

Quantitative analysis of interferon α/β receptor mRNA in the liver of patients with chronic hepatitis C: Correlation with serum hepatitis C virus-RNA levels and response to treatment with interferon

We analysed the expression of interferon (IFN) α/β receptor mRNA in the liver of patients with chronic hepatitis C and examined the relationship between the expression of this receptor gene and the level of hepatitis C virus (HCV)-RNA as well as the response to 16 weeks of 6 × 10⁶ units IFN. The mean level of IFNα/β receptor mRNA in patients with chronic HCV infection (expressed as δ cycle; 10.8±1.9 (mean±SD); n = 39) was significantly higher than that of control subjects (9.4±0.5; n=6; P<0.01). There was a significant negative correlation between the level of IFNα/β receptor mRNA and serum HCV-RNA in 39 patients with chronic hepatitis C (R=-0.546; P<0.01). The mean level of IFNα/β receptor mRNA in six patients who showed a complete response to IFN therapy (12.3±1.6) was higher than that of 15 patients who failed to respond to therapy (10.1±1.5; P< 0.01). Our results are consistent with the suggestion that the anti-viral activity of IFN depends on the level of the IFNα/β receptor on hepatocytes in patients with chronic hepatitis C.