scholarly journals Gonadotropin-secreting cells in ovariectomized rats treated with different oestrogen receptor ligands: a modulatory role for ERβ in the gonadotrope?

2006 ◽  
Vol 188 (2) ◽  
pp. 167-177 ◽  
Author(s):  
J E Sánchez-Criado ◽  
J Martín de las Mulas ◽  
C Bellido ◽  
V M Navarro ◽  
R Aguilar ◽  
...  
Keyword(s):  
Oestrogen Receptor ◽  
Light And Electron Microscopy ◽  
Ovariectomized Rats ◽  
Secretory Process ◽  
Oestrogen Receptors ◽  
Receptor Ligands ◽  
Structural Reorganization ◽  
Relative Contribution ◽  
Oestradiol Benzoate ◽  
Lh Secretion

In the rat, oestrogen is a key regulator of gonadotrophin synthesis and release through activation of oestrogen receptors (ERs). Gonadotropes express α and β isoforms of ER and both can activate transcription in response to oestrogen. These experiments were aimed at evaluating the relative contribution of ERα and ERβ on gonadotrope morphology, progesterone receptor (PR) expression and LH secretion. Ovariectomized rats were daily injected over 3 days with 25 μg oestradiol benzoate, 0.3 or 1.5 mg of the selective ERα agonist propylpyrazole triol (PPT) with or without 1.5, 3.0 or 4.5 mg of the selective ERβ agonist diarylpropionitrile (DPN), DPN alone, and 0.3 or 3 mg of tamoxifen. Controls were given 0.2 ml oil. Serum concentration and pituitary content of LH, gonadotrope PR expression, pituitary PR content, and gonadotrope morphology were analyzed by RIA, immunohistochemistry, Western blotting and light and electron microscopy, respectively. Results showed that PPT reversed all consequences of ovariectomy, DPN mimicked the effects of PPT except for its LH-releasing action and tamoxifen had ERα-like responses. When combined with PPT, DPN attenuated ERα effects without interfering with its LH-releasing activity. Oestradiol benzoate had similar effects to those of combined PPT and DPN. It is suggested that (i) the structural reorganization of the cytoplasmic organelles provided by oestrogen, and the shrinkage of the ovariectomy-induced hypertrophy of gonadotropes, which precedes the expression of PR, are evoked by ERα and modulated, in a ying–yang fashion, by ERβ; and (ii) the oestrogen-dependent exocytosis of LH, the final step in the secretory process, is dependent on ERα exclusively.

Adrenal progesterone facilitates the negative feedback of oestrogen on LH release in ovariectomized rats

1993 ◽  
Vol 139 (2) ◽  
pp. 253-258 ◽  
Author(s):  
A. M. Salicioni ◽  
R. W. Carón ◽  
R. P. Deis
Keyword(s):  
Ovariectomized Rats ◽  
Adrenal Steroids ◽  
Serum Progesterone ◽  
Oestrogen Treatment ◽  
Ovx Rats ◽  
Serum Lh ◽  
Oestradiol Benzoate ◽  
Lh Release ◽  
Lh Secretion

ABSTRACT There is evidence that the adrenals play a role in the regulation of the synthesis and release of gonadotrophins in various vertebrates. The aim of this study was to determine the part played by adrenal steroids, with special reference to progesterone, on the concentration of LH in ovariectomized (OVX) and oestrogen-primed rats. OVX rats received a single s.c. injection of vehicle or oestradiol benzoate (OB, 20 μg/rat). This day was designated as day 0. Three or four days later (day 3–day 4), the rats were treated with mifepristone (10 mg/kg) or with two doses of progesterone antiserum and blood samples were obtained at 13.00 and 18.00 h. OB treatment of OVX rats reduced serum LH at 13.00 h and 18.00 h on day 3 but only at 13.00 h on day 4. The administration of mifepristone at 08.00 h to OVX and oestrogen-treated rats induced a significant increase in serum LH at 18.00 h on days 3 and 4, without modifying the values at 13.00 h. When mifepristone was given at 13.00 h a much larger increase in serum LH was obtained at 18.00 h. In OVX and oestrogen-treated rats, adrenalectomy on day 2 (08.00–09.00 h) induced an increase in serum LH at 18.00 h similar to that observed in the OVX and oestrogen-primed rats after mifepristone treatment. In order to determine the specificity of the effect of mifepristone, a group of OVX and oestrogentreated rats was injected with progesterone antiserum at 08.00 and 13.00 h on day 3. Serum LH concentrations at 13.00 and 18.00 h on day 3 were similar to values obtained in OVX rats treated with oestrogen and mifepristone. Serum progesterone was measured at 08.00 and 13.00 h in OVX and OVX and oestrogenprimed rats. At both times, values were similar in OVX rats but oestrogen treatment significantly increased serum progesterone levels. The important role of adrenal progesterone on the regulation of LH secretion in OVX and oestrogen-primed rats is evident from these results. Blocking progesterone action at the receptor level, we showed that OB significantly increased LH values at 18.00 h. On the basis of these studies it is tempting to speculate on the possibility of an inhibitory or stimulatory effect of oestrogen on serum LH concentration in OVX rats, according to the presence or absence of adrenal progesterone action. Journal of Endocrinology (1993) 139, 253–258

scholarly journals Gonadotrope oestrogen receptor-α and -β and progesterone receptor immunoreactivity after ovariectomy and exposure to oestradiol benzoate, tamoxifen or raloxifene in the rat: correlation with LH secretion

2005 ◽  
Vol 184 (1) ◽  
pp. 59-68 ◽  
Author(s):  
J E Sánchez-Criado ◽  
J Martín de las Mulas ◽  
C Bellido ◽  
R Aguilar ◽  
J C Garrido-Gracia
Keyword(s):  
Progesterone Receptor ◽  
Oestrogen Receptor ◽  
Immunohistochemical Expression ◽  
Stimulatory Action ◽  
Receptor Modulator ◽  
Ovx Rats ◽  
Oestradiol Benzoate ◽  
Cycle Dependent ◽  
Lh Secretion ◽  
Selective Oestrogen Receptor Modulator

The selective oestrogen receptor modulator (SERM) tamoxifen (TX) has agonist/antagonist actions on LH secretion in the rat. Whereas in the absence of oestrogens TX elicits progesterone receptor (PR)-dependent GnRH self-priming, it antagonizes oestrogen-stimulatory action on LH secretion. The aim of these experiments was to explore whether TX treatment-induced differential expression of oestrogen receptor (ER)α and ERβ in the gonadotrope may determine its agonist effect on LH secretion. In the first experiment, basal LH secretion, GnRH-stimulated LH secretion and PR-dependent GnRH self-priming were determined in incubated pituitaries from ovariectomized (OVX) rats treated with oestradiol benzoate (EB), TX or raloxifene (RX). Cycling rats in metoestrus or pro-oestrus were used as basic controls. As in pro-oestrus, pituitaries from OVX rats treated with EB exhibited GnRH-stimulated LH secretion, immunohistochemical PR expression and GnRH self-priming. While RX had no effect on these parameters, TX induced PR expression and GnRH self-priming. GnRH self-priming was absent in pituitaries incubated with the antiprogestin ZK299. In the second experiment, we evaluated the immunohistochemical expression of ERα and ERβ in gonadotropes of cycling rats and OVX rats treated with EB, TX or RX. We found that while ERα expression was similar in all six groups, ERα expression was oestrous cycle dependent. Moreover, ERα expression in gonadotropes of TX-treated rats was as high as that found in pro-oestrus, while ERα expression in the gonadotropes of RX-treated rats was lower than in metoestrous or pro-oestrous pituitaries. These results suggest that, in the absence of the cognate ligand, TX, unlike RX, may regulate LH secretion through the ERα subtype in gonadotropes.

Dissociation between the ovarian factors controlling sexual receptivity and preovulatory secretion of LH in cyclic female rats

1987 ◽  
Vol 112 (1) ◽  
pp. 133-138 ◽  
Author(s):  
P. Södersten ◽  
P. Eneroth
Keyword(s):  
Sexual Behaviour ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Sexual Receptivity ◽  
Serum Progesterone ◽  
Lh Surge ◽  
Oestradiol Benzoate ◽  
Lh Release ◽  
Lh Secretion ◽  
Intact Rats

ABSTRACT Ovariectomy and treatment with oestradiol benzoate (10 μg OB) on the day before behavioural oestrus eliminated the preovulatory surge of LH and reduced the level of sexual receptivity on the following day. Sexual behaviour, but not the LH surge, was restored by progesterone (0·5 mg) given 18 h later. Injection of OB on the day after behavioural oestrus induced a small release of LH and normal sexual behaviour on the following day. Ovariectomy on the day after behavioural oestrus reduced the stimulatory effect of OB on sexual behaviour and eliminated its weakly stimulatory effect on LH release. Sexual behaviour, but not the small LH surge, was restored in these animals by progesterone (0·5 mg) given 18 h later. Treatment of rats ovariectomized 2 days before the day of the LH surge with implants containing oestradiol or injections of oestradiol (1 μg) induced LH surges but the amplitudes of these LH surges were much smaller than those of the normal LH surge. Treatment of intact rats with OB increased serum progesterone levels 24 h later, an effect which was eliminated by ovariectomy. Injections of LH (20 μg) into intact rats on the day after behavioural oestrus also increased serum progesterone concentrations but failed to stimulate sexual behaviour. It is suggested that OB treatment of intact rats on the day after behavioural oestrus stimulates sexual behaviour by inducing a surge of LH secretion which activates ovarian secretion of progesterone. Thus, oestrogen and progesterone but not the LH surge are essential for sexual behaviour. Whereas oestradiol and progesterone restore normal sexual behaviour in ovariectomized rats, additional ovarian factors may be required for induction of normal LH surges. J. Endocr. (1987) 112, 133–138

PROGESTERONE-INDUCED OESTROGEN RECEPTORS IN THE RAT UTERUS

1978 ◽  
Vol 76 (1) ◽  
pp. 145-154 ◽  
Author(s):  
DOMINIQUE MARTEL ◽  
ALEXANDRE PSYCHOYOS
Keyword(s):  
Physicochemical Properties ◽  
Oestrogen Receptor ◽  
Sedimentation Coefficient ◽  
Kinetic Constants ◽  
Ovariectomized Rats ◽  
Oestrogen Receptors ◽  
Rat Uterus ◽  
Receptor Molecule

SUMMARY In ovariectomized rats progesterone acts like oestradiol at the endometrial, but not at the myometrial level, by increasing the number of oestrogen receptors in the cytoplasm. After 3 days of progesterone priming, the number of endometrial oestrogen receptors was found to be three times higher (P<0·05, Student's t-test) than control values. This progesterone-induced oestrogen receptor molecule appears identical in its physicochemical properties (sedimentation coefficient, kinetic constants, steroid specificity) to that induced in the endometrium and myometrium under the influence of oestradiol. However, in the myometrium progesterone acts antagonistically reducing significantly (P< 0·001, Student's t-test) the oestradiol-induced increase in the number of oestrogen receptors.

Vasoactive intestinal peptide inhibits the steroid-induced LH surge in the ovariectomized rat

1992 ◽  
Vol 133 (3) ◽  
pp. 433-437 ◽  
Author(s):  
R. F. Weick ◽  
K. M. Stobie
Keyword(s):  
Vasoactive Intestinal Peptide ◽  
Critical Period ◽  
Control Sample ◽  
Ovariectomized Rats ◽  
Lh Surge ◽  
The Third ◽  
Oestradiol Benzoate ◽  
Short Time ◽  
Lh Secretion ◽  
Secretion Rates

ABSTRACT The LH surge was induced in ovariectomized rats by sequential treatment with oestradiol benzoate and progesterone. Vasoactive intestinal peptide (VIP) or saline was infused into the third cerebral ventricle from 13.30 to 16.30 h on the afternoon of the anticipated LH surge. Two blood samples were taken by jugular puncture from each animal, one at 12.00 h as a control sample and the other at 16.00, 18.00, 20.00 or 22.00 h. Saline-infused animals showed a normal LH surge, with mean plasma LH concentrations reaching a peak at 18.00 h, declining by 20.00 h and reaching control (12.00 h) levels by 22.00 h. Plasma LH in animals infused with VIP was not significantly higher than control levels at 16.00 or 18.00 h. By 20.00 h, mean LH levels in VIP-infused rats had risen to the levels seen at that time in saline-infused rats, and by 22.00 h LH had returned to control levels in VIP-infused animals. We interpret these findings to mean that VIP inhibits LH secretion during the LH surge. It does not block the surge completely, as pentobarbital during the critical period would have done; nor does VIP appear to affect the timing of the LH surge. Rather, VIP inhibits the increased LH secretion rates of the LH surge only during the period of VIP treatment and for a short time afterward. Journal of Endocrinology (1992) 133, 433–437

SECRETION OF LUTEINIZING HORMONE IN OVARIECTOMIZED ADULT RATS TREATED NEONATALLY WITH MONOSODIUM GLUTAMATE

1981 ◽  
Vol 91 (2) ◽  
pp. 341-346 ◽  
Author(s):  
R. G. DYER ◽  
R. F. WEICK ◽  
S. MANSFIELD ◽  
H. CORBET
Keyword(s):  
Monosodium Glutamate ◽  
Pulse Height ◽  
Treated Group ◽  
Experimental Manipulation ◽  
Ovariectomized Rats ◽  
Adult Rats ◽  
Blood Samples ◽  
Oestradiol Benzoate ◽  
And Control ◽  
Lh Secretion

We have studied the possible effects of monosodium glutamate (MSG) on LH secretion in ovariectomized rats. In experiment 1 MSG-treated and control rats were given oestradiol benzoate at noon and 72 h later half the rats in each group were given a second injection of oestradiol benzoate or progesterone. Blood samples were taken immediately before and 6 h after these i.m. injections. At 78 h there were no significant differences in plasma LH concentration measured in the two groups of rats given progesterone or in the two groups given a second injection of oestradiol benzoate although for both MSG-treated and control rats progesterone produced a significantly (P < 0·01) greater LH surge than did oestradiol benzoate. In experiment 2 100 μl blood samples were collected at 5-min intervals for up to 3 h from MSG-treated and control rats. For rats showing more than one pulsatile discharge of LH, peak and trough values for plasma LH concentrations were not significantly influenced by MSG treatment. However the mean pulse height was significantly (P < 0·001) greater in the MSG-treated group than in control rats. Pulsatile release stopped more quickly in the MSG-treated rats and their mean plasma LH concentration after 120 min of blood sampling was significantly (P < 0·05) lower than that obtained in the control animals. Thus, although some aspects of LH secretion seem to be significantly different in MSG-treated rats, these effects may result from the greater sensitivity of the MSG-treated animals to experimental manipulation.

UTERINE OESTROGEN AND PROGESTERONE RECEPTORS IN THE OVARIECTOMIZED RAT

1981 ◽  
Vol 91 (2) ◽  
pp. 281-287 ◽  
Author(s):  
ANDREA MANNI ◽  
REBECCA BAKER ◽  
B. M. ARAFAH ◽  
O. H. PEARSON
Keyword(s):  
Progesterone Receptors ◽  
Total Cell ◽  
Ovariectomized Rats ◽  
Oestrogen Receptors ◽  
Rat Uterus ◽  
Experimental Conditions ◽  
Cell Content ◽  
Transient Rise ◽  
Additional Group ◽  
Oestradiol Benzoate

The effect was studied of repeated injections of oestradiol-17β (5, 10, 25, 50 μg) given for various lengths of time (3, 5, 9 days) on total cell content of oestrogen receptors and cytosol progesterone receptors in the uteri of ovariectomized rats. An additional group of rats was injected daily with 50 μg oestradiol benzoate (OB) for 9 days in order to achieve a more sustained concentration of oestradiol in the blood. Injections were begun 24 h after ovariectomy and the rats were killed 24 h after the last injection. Daily administration of 5 μg oestradiol prevented the initial transient rise in oestrogen receptors which was observed in the uteri of untreated rats after ovariectomy. Repeated injections of 10 μg oestrogen produced an initial lowering in oestrogen receptors after 3 days of treatment which was followed by a prompt rise at 5 and 9 days when treatment was continued. A significant reduction in oestrogen receptors occurred at all times studied when rats were injected daily with 25 and 50 μg oestradiol. A more profound reduction in oestrogen receptors was observed in the group of rats treated for 9 days with 50 μg OB. Synthesis of progesterone receptors was stimulated by all doses of oestrogen studied. Concentrations of progesterone receptors were significantly higher after 3 and 5 days of treatment with 25 and 50 μg oestrogen. After 9 days of treatment, however, concentrations of progesterone receptors were virtually identical in all treated groups, including the group treated with OB. We have concluded that large doses of oestrogen significantly decrease oestrogen receptor content in the rat uterus, especially when OB is used. The degree of reduction, however, is only moderate under these experimental conditions and is insufficient to inhibit synthesis of progesterone receptors.

scholarly journals The integrated action of oestrogen receptor isoforms and sites with progesterone receptor in the gonadotrope modulates LH secretion: evidence from tamoxifen-treated ovariectomized rats

2007 ◽  
Vol 193 (1) ◽  
pp. 107-119 ◽  
Author(s):  
José C Garrido-Gracia ◽  
Ana Gordon ◽  
Carmina Bellido ◽  
Rafaela Aguilar ◽  
Inmaculada Barranco ◽  
...  
Keyword(s):  
Progesterone Receptor ◽  
Oestrogen Receptor ◽  
Ovariectomized Rats ◽  
The Past ◽  
Receptor Isoforms ◽  
Ovx Rats ◽  
Lh Release ◽  
Lh Releasing Hormone ◽  
Lh Secretion

The specific role of each oestrogen receptor (ER) isoform (α and β ) and site (nucleus and plasma membrane) in LH release was determined in ovariectomized (OVX) rats injected over 6 days (days 15–20 after OVX) with a saturating dose (3 mg/day) of tamoxifen (TX), a selective ER modulator with nuclear ERα agonist actions in the absence of oestrogen. This pharmacological effect of TX was demonstrated by the fact that it was blocked by the selective ERα antagonist methyl-piperidinopyrazole. Over the past 3 days of the 6-day TX treatment, rats received either 25 μg/day oestradiol benzoate (EB), 1.5 mg/day selective ERα agonist propylpyrazole triol (PPT) and the selective ERβ agonist diarylpropionitrile (DPN), or a single 3 mg injection of the antiprogestin onapristone (ZK299) administered on day 20. Blood samples were taken to determine basal and progesterone receptor (PR)-dependent LH-releasing hormone (LHRH)-stimulated LH secretion and to evaluate LHRH self-priming, the property of LHRH that increases gonadotrope responsiveness to itself. Blood LH concentration was determined by RIA and gonadotrope PR expression by immunohistochemistry. Results showed that i) EB and DPN potentiated the negative feedback of TX on basal LH release; ii) DPN reduced TX-induced PR expression; iii) EB and PPT blocked TX-elicited LHRH self-priming and iv) ZK299 reduced LHRH-stimulated LH secretion and blocked LHRH self-priming. These observations suggest that oestrogen action on LH secretion in the rat is exerted at the classic ERα pool and that this action might be modulated by both ERβ and membrane ERα through their effects on PR expression and action respectively.

scholarly journals The nuclear oestrogen receptor in the female rat. Effects of oestradiol administration during the oestrous cycle on the uterus and contrasting effects of progesterone on the uterus and hypothalamus

1981 ◽  
Vol 198 (2) ◽  
pp. 385-389 ◽  
Author(s):  
S Thrower ◽  
L Lim
Keyword(s):  
Adult Female ◽  
Oestrogen Receptor ◽  
Oestrous Cycle ◽  
Ovariectomized Rats ◽  
Female Rat ◽  
Oestrogen Receptors ◽  
Adult Rat ◽  
Receptor Interactions ◽  
Neural Tissues

Oestradiol administration to immature or ovariectomized rats has been reported to increase the uterine content of long-term nuclear oestrogen receptors. However, in the intact adult female rat, oestradiol administration did not increase the concentration of long-term nuclear oestrogen receptors at all phases of the oestrous cycle. Progesterone administration to rats in late dioestrus did not affect the concentration of uterine nuclear oestrogen receptors 24 h later, although it did prevent the normal cyclic increase at pro-oestrus in the concentration of hypothalamic nuclear oestrogen receptors. Our results therefore show that in the intact adult rat, factors other than the concentration of progesterone or oestradiol determine the nuclear concentration of oestrogen receptors in the uterus. They also demonstrate differences between neural and non-neural tissues in the regulation of oestrogen-receptor interactions.

Oestrogen receptors and effects of oestradiol administration on mRNA synthesis in the limbic system of the neonatal female rat

1989 ◽  
Vol 120 (1) ◽  
pp. 83-88 ◽  
Author(s):  
B. D. Greenstein ◽  
I. M. Adcock
Keyword(s):  
Sexual Dimorphism ◽  
Rat Brain ◽  
Limbic System ◽  
Oestrogen Receptor ◽  
Neonatal Rat ◽  
Oestrogen Receptors ◽  
Mrna Synthesis ◽  
Isoelectric Focussing ◽  
Oestradiol Benzoate ◽  
Neonatal Rat Brain

ABSTRACT There is sexual dimorphism of specific species of mRNA in the neonatal rat brain and this sexual dimorphism may be imprinted by steroids of testicular origin during the perinatal period. According to current theories, only aromatizable androgens may cause sexual differentiation of sexual behaviour and function in the adult. The effects of oestradiol benzoate on mRNA synthesis in the neonatal female limbic system were therefore studied. In addition, cytosolic and nuclear oestrogen receptors were measured after administration of testosterone propionate, oestradiol benzoate or dihydrotestosterone (DHT). An attempt was made to distinguish between the brain oestrogen receptor and the plasma oestrogen-binding protein, alphafoetoprotein (AFP) by isoelectric focussing. After injection of 50 μg oestradiol benzoate s.c. to neonatal female rats, the expression of mRNA coding for sexually dimorphic proteins appeared to be changed to a male-type pattern. The overall density of labelling was noticeably greater and specific changes in labelled proteins were observed. These effects were observed within 3 h of injection. Both testosterone and oestradiol caused a marked depletion of cytosolic oestrogen receptors in the limbic system whereas DHT was ineffective in this respect. Nuclear receptors were present in equal abundance in male- and female-derived nuclei and only oestradiol was able to cause a significant (P < 0·025) increase in nuclear oestrogen receptors. The receptor and AFP could be distinguished by isoelectric focussing, since the pI of the receptor was 7·05, while that of AFP was 4·5. These results are consistent with the possibility that oestradiol alters transcription in the neonatal rat brain and may do this through the oestrogen receptor. Nevertheless, it is also possible that oestradiol could alter post-transcriptional events such as the stability of mRNA or the binding of tRNA to the polysomal complex. Journal of Endocrinology (1989) 120, 83–88

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