Effect of estradiol on the secretion of LH in the GnRH-pretreated rat after treatment with the GnRH-antagonist, Org 30093

1988 ◽  
Vol 119 (4) ◽  
pp. 582-588
Author(s):  
G. A. Schuiling ◽  
N. Valkhof ◽  
T. R. Koiter
Keyword(s):  
Pituitary Gland ◽  
Gnrh Antagonist ◽  
Plasma Concentrations ◽  
Estradiol Benzoate ◽  
The Other ◽  
Gnrh Analogue ◽  
Before And After ◽  
Pituitary Glands ◽  
Lh Secretion

Abstract. LH responses induced in the long-term ovariectomized rat by GnRH or GnRH agonistic analogue are augmented by E2. The augmentation by E2 does not occur during, but after termination of GnRH pretreatment. In this study it was investigated whether the augmenting effect of E2 develops also in the GnRH-pretreated rat when the animals were treated with GnRH antagonistic analogue. Two weeks after ovariectomy rats were treated for 10 days with 250 ng GnRH/h (GnRH-rats), released by sc implanted osmotic minipumps. Control rats received a Silastic 'sham pump'. Rats were simultaneously treated with solvent (oil) or estradiol benzoate (EB, 3 μg, sc). Each group of rats was divided into two subgroups, one receiving solvent, the other the GnRH antagonist, Org 30093 (ANT, 100 μg/injection) on 3 consecutive days. In Experiment 1, the pituitary LH content and the LH secretion following stimulation with the agonistic GnRH analogue buserelin, were measured, in Experiment 2, the plasma concentrations of LH before and after cessation of ANT treatment. The effects of treatment with GnRH, EB and ANT were studied on the basis of 1) the height of the maximal LH response and 2) the halfmaximally effective dose (ed 50) of buserelin. Experiment 1 revealed that GnRH depleted the pitutiary gland to about 42% of its original LH content. In EB-treated GnRH-rats the depletion was even stronger (to 14%). After ANT treatment, the pituitary glands of the GnRH-rats were (partly) repleted (oil: to 65%; EB: to 31%). ANT and EB had no effect on the pituitary LH content in control rats. EB increased the maximal LH response in control rats but not in GnRH-rats. ANT increased the maximal LH response to buserelin in oil-injected control rats as well as in oil- and EB-treated GnRH-rats. In these latter two groups, the increase of the maximal LH response was equally large. However, there was an effect of EB on the ed 50 of buserelin during ANT treatment, the pituitary gland of the EB-treated GnRH-rats had become more sensitive to GnRH. Experiment 2 revealed that GnRH pretreatment reduced the plasma LH concentrations to about 49% of the control levels. EB and ANT, too, lowered the plasma LH concentrations (to about 25%). Neither EB nor ANT, alone or in combination, changed the plasma LH concentrations in GnRH-rats. After cessation of ANT treatment, the plasma LH levels of the oil-injected control rats slowly returned to pretreatment levels, but those of the EB-treated control rats remained suppressed. In the GnRH-rats the reverse was seen: after cessation of ANT treatment, peaks of LH appeared in the plasma of the EB-treated rats, but not in the oil-injected. It is concluded that 1) treatment with ANT is not fully equivalent to termination of GnRH administration because it antagonizes the effects of GnRH only in part: 2) ANT has an intrinsic augmenting effect on the pituitary GnRH-responsiveness, and 3) owing to E2-induced sensitization of the pituitary gland, peaks of LH appear in the plasma of GnRH-rats but not of control rats after termination of ANT treatment.

Effects of long-term administration of high doses of medroxyprogesterone acetate on hormone receptors and target organs in the female rat

1984 ◽  
Vol 103 (3) ◽  
pp. 287-293 ◽  
Author(s):  
F. Di Carlo ◽  
S. Racca ◽  
G. Conti ◽  
E. Gallo ◽  
G. Muccioli ◽  
...  
Keyword(s):  
Pituitary Gland ◽  
Medroxyprogesterone Acetate ◽  
Prolactin Receptor ◽  
Female Rats ◽  
Serum Prolactin ◽  
Target Organs ◽  
Term Administration ◽  
Pituitary Glands ◽  
High Doses

ABSTRACT The changes in oestrogen, progesterone and prolactin receptor levels in target organs, and the macroscopic and microscopic modifications of uterus, ovary, adrenal and pituitary gland induced by long-term administration of high doses of medroxyprogesterone acetate (MPA) were investigated in female rats. Medroxyprogesterone acetate was injected i.m. for 30 days at daily doses of 7·5, 15 and 75 mg/kg. Oestrogen and/or progesterone-binding capacities were remarkably reduced at all doses of MPA used both in the uterus and pituitary gland. Furthermore, MPA caused a very evident reduction in the weight of pituitary glands, ovaries, adrenals and uterus. In all MPA-treated rats corpora lutea were absent from the ovaries, whereas the adrenals showed a significant reduction in the thickness of the cortex. In accordance with this, there was no evidence of ACTH-producing cells in the pituitary glands. Prolactin-producing cells were also absent, while GH-producing cells were present. Serum prolactin levels were significantly reduced at all doses of MPA used. A dramatic reduction of prolactin receptor concentrations was observed in the liver and the ovaries of MPA-treated rats. The results suggest that MPA acts as an antioestrogenic drug both by reducing the number of oestrogen receptors in target tissues and by changing the structure (and perhaps the function) of those organs (pituitary glands, ovaries and adrenals) which are, directly or indirectly, a source of oestrogens. The decreased synthesis of prolactin and the reduction of the number of prolactin receptors (which, on the contrary, are both increased by oestrogens) might be considered as additional antioestrogenic effects of MPA. J. Endocr. (1984) 103, 287–293

LH SECRETION DURING LONG-TERM EXPOSURE OF PITUITARY GLANDS TO LH-RH

1981 ◽  
pp. 65-71
Author(s):  
G.P. van Rees ◽  
J.A.M.J. van Dieten ◽  
A.M.I. Tijssen ◽  
J. de Koning
Keyword(s):  
Pituitary Glands ◽  
Lh Rh ◽  
Lh Secretion

scholarly journals Inhibin is an important factor in the regulation of FSH secretion in the adult male hamster

2000 ◽  
Vol 278 (4) ◽  
pp. E744-E751 ◽  
Author(s):  
Hisashi Kishi ◽  
Mariko Itoh ◽  
Sachiko Wada ◽  
Yoko Yukinari ◽  
Yumiko Tanaka ◽  
...  
Keyword(s):  
Adult Male ◽  
Leydig Cells ◽  
Initial Level ◽  
Plasma Concentrations ◽  
Plasma Testosterone ◽  
Gonadotropin Secretion ◽  
Α Subunit ◽  
Male Golden Hamsters ◽  
Lh Secretion

We investigated the importance of inhibin and testosterone in the regulation of gonadotropin secretion in adult male golden hamsters ( Mesocricetus auratus). After castration, plasma concentrations of inhibin and testosterone were reduced to undetectable, whereas plasma follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were increased. After hemicastration, plasma FSH and LH increased moderately and plasma inhibin decreased to one-half its initial level. Plasma testosterone levels in hemicastrated animals decreased 3 h after hemicastration but returned to those in sham-operated animals at 6 h. Plasma LH in the castrated hamster declined comparably to intact animals with testosterone treatment; plasma FSH also decreased but still remained at levels higher than those in intact animals. After treatment with inhibin in long-term-castrated animals, plasma FSH decreased, whereas plasma LH was not altered. Intact males treated with flutamide, an anti-androgen, showed a significant increase in plasma LH but not in FSH. On the other hand, treatment with anti-inhibin serum induced a significant elevation in plasma FSH, but not in LH. Using immunohistochemistry, we showed that the inhibin α-subunit was localized to both Sertoli and Leydig cells. The present study in adult male hamsters indicates that FSH secretion is regulated mainly by inhibin, presumably from Sertoli and Leydig cells, and that LH secretion is controlled primarily by androgens produced from the Leydig cells. This situation is more similar to that of primates than of rats.

scholarly journals Impact of adopting a vegan diet or an olestra supplementation on plasma organochlorine concentrations: results from two pilot studies

2009 ◽  
Vol 103 (10) ◽  
pp. 1433-1441 ◽  
Author(s):  
Hélène Arguin ◽  
Marina Sánchez ◽  
George A. Bray ◽  
Jennifer C. Lovejoy ◽  
John C. Peters ◽  
...  
Keyword(s):  
Weight Loss ◽  
Polychlorinated Biphenyl ◽  
Plasma Concentrations ◽  
Dietary Lipids ◽  
The Body ◽  
The Other ◽  
Vegan Diet ◽  
Standard Group ◽  
Pilot Studies ◽  
Before And After

The aim of these studies was to evaluate the potential of some nutritional approaches to prevent or reduce the body load of organochlorines (OC) in humans. Study 1 compared plasma OC concentrations between vegans and omnivores while study 2 verified if the dietary fat substitute olestra could prevent the increase in OC concentrations that is generally observed in response to a weight-reducing programme. In study 1, nine vegans and fifteen omnivores were recruited and the concentrations of twenty-six OC (β-hexachlorocyclohexane (β-HCH), p, p′-dichlorodiphenyldichloroethane (p, p′-DDE), p, p′-dichlorodiphenyltrichloroethane (p, p′-DDT), hexachlorobenzene, mirex, aldrin, α-chlordane, γ-chlordane, oxychlordane, cis-nonachlor, trans-nonachlor, polychlorinated biphenyl (PCB) nos. 28, 52, 99, 101, 105, 118, 128, 138, 153, 156, 170, 180, 183 and 187, and aroclor 1260) were determined. In study 2, the concentrations of these twenty-six OC were measured before and after weight loss over 3 months in thirty-seven obese men assigned to one of the following treatments: standard group (33 % fat diet; n 13), fat-reduced group (25 % fat diet; n 14) or fat-substituted group (1/3 of dietary lipids substituted by olestra; n 10). In study 1, plasma concentrations of five OC compounds (aroclor 1260 and PCB 99, PCB 138, PCB 153 and PCB 180) were significantly lower in vegans compared with omnivores. In study 2, β-HCH was the only OC which decreased in the fat-substituted group while increasing in the other two groups (P = 0·045). In conclusion, there was a trend toward lesser contamination in vegans than in omnivores, and olestra had a favourable influence on β-HCH but did not prevent plasma hyperconcentration of the other OC during ongoing weight loss.

Membranous Layers of the Pituitary Gland: Histological Anatomic Study and Related Clinical Issues

2009 ◽  
Vol 64 (suppl_1) ◽  
pp. ONS1-ONS10 ◽  
Author(s):  
Qi Songtao ◽  
Lu Yuntao ◽  
Pan Jun ◽  
Huang Chuanping ◽  
Shi Xiaofeng
Keyword(s):  
Pituitary Gland ◽  
Lamina Propria ◽  
Internal Carotid ◽  
The Other ◽  
Medial Wall ◽  
Lateral Part ◽  
Fibrous Layer ◽  
Human Pituitary ◽  
Human Pituitary Gland ◽  
Pituitary Glands

Abstract Objective: The purpose of this study was to examine the membranous layers of the human pituitary gland and their relationships with invasive adenomas. Methods: Histological and microdissection techniques were used to study 8 fetal and 10 adult human cadavers, respectively. The distribution of the membranous layers was observed, and their thickness was measured. The results were analyzed histologically and anatomically. Results: In all specimens, the pituitary glands were found to be coated by 2 membranous layers, the inner layer being referred to here as the lamina propria and the outer as the pituitary capsule. In all specimens, the 2 membranes were intact with no histological defects. An interstice or cavity between the 2 layers was found on the surface of the adenohypophysis. However, as these 2 layers got closer and closer to each other, they began to adhere on the surface of the neurohypophysis. The thickness of the pituitary capsule was not constant like that of the lamina propria: the inferolateral part of the capsule was thicker than the other parts. The medial wall of the cavernous sinus (CS) was also a bilayered membrane just like the other CS walls: the 2 layers of the medial CS wall were composed of the lateral part of the pituitary capsule and the fibrous layer. Many fibrous trabeculae arising from this fibrous layer divided the CS into several small venous spaces and connected the internal carotid arteries with the medial wall. Conclusion: The terminology for the 2 membranous layers, the lamina propria and the pituitary capsule, seemed to be more appropriate and representative of the histological features of the pituitary layers. The lateral part of the capsule and the fibrous layer constituted the medial wall of the CS, which has a superior part that is weaker than the thicker inferior part. It is still difficult to postulate the criteria needed to predict CS invasion. However, the distance between the 2 sides of the internal carotid artery might be another predictive criterion to preoperatively diagnose CS invasion by adenomas. Enhanced knowledge of these membranes may be of assistance in finding a useful criterion.

GONADO-PITUITARY RELATIONSHIPS IN THE FETAL MOUSE AT VARIOUS TIMES DURING SEXUAL DIFFERENTIATION

1980 ◽  
Vol 86 (3) ◽  
pp. 483-488 ◽  
Author(s):  
G. POINTIS ◽  
M.-T. LATREILLE ◽  
L. CEDARD
Keyword(s):  
Sexual Differentiation ◽  
Feedback Inhibition ◽  
Plasma Concentrations ◽  
Male Mice ◽  
Male And Female ◽  
Fetal Mouse ◽  
Female Mice ◽  
Fetal Mice ◽  
Pituitary Glands ◽  
Lh Secretion

Levels of testosterone in plasma and concentrations of LH in both plasma and pituitary glands of fetal mice aged 14, 16 and 18 days were measured by radioimmunoassays in a representative number of fetuses. During this period levels of testosterone in the plasma of male mice were significantly higher than those in the females. Levels of testosterone in plasma of male mice increased from day 14 to day 16 of gestation and decreased on day 1 before parturition. Plasma concentrations of LH remained undetectable in male and female fetuses until day 16 of gestation. Levels of LH rose slightly in both sexes in later gestation, but still remained significantly lower in the plasma of male fetuses on days 17–18. In contrast, higher but not significantly different concentrations of LH were observed in pituitary glands from days 14 to 18 in male compared with female mice. These observations suggest that the high levels of testosterone in the plasma of male fetal mice might be responsible for feedback inhibition of LH secretion during the last days of gestation.

Isolated ACTH deficiency accompanied by 'primary hypothyroidism' and hyperprolactinaemia

1983 ◽  
Vol 104 (4) ◽  
pp. 397-401 ◽  
Author(s):  
Tadayoshi Yoshida ◽  
Tetsuya Arai ◽  
Jinpei Sugano ◽  
Hiroshi Yarita ◽  
Hideo Yanagisawa
Keyword(s):  
Pituitary Gland ◽  
Primary Hypothyroidism ◽  
Hormonal Changes ◽  
Plasma Acth ◽  
Isolated Acth Deficiency ◽  
Acth Deficiency ◽  
Corticotrophin Releasing Factor ◽  
Lysine Vasopressin ◽  
Before And After

Abstract. A 55 year old man with isolated ACTH deficiency is reported. The lesion would appear to be located in the pituitary gland since plasma ACTH and cortisol did not respond to lysine vasopressin and corticotrophin releasing factor (CRF). A fall in T4, a rise in basal values of TSH, prolactin (Prl), LH and FSH, excessive responses of TSH and Prl to TRH, and hyperreactive responses of LH and FSH to LRH were observed. These hormonal changes were examined before and after administration of cortisol. The abnormality in these hormones might be caused by deficiency of long-term glucocorticoid.

Mechanisms responsible for suppression of FSH and LH during lactation in the rat

1991 ◽  
Vol 129 (1) ◽  
pp. 119-130 ◽  
Author(s):  
K. Taya ◽  
S. Sasamoto
Keyword(s):  
Plasma Concentrations ◽  
The Other ◽  
Primary Role ◽  
Ovarian Steroids ◽  
Unilateral Ovariectomy ◽  
Peripheral Plasma ◽  
The Mean ◽  
Lh Secretion ◽  
Ovarian Inhibin ◽  
Venous Plasma

ABSTRACT Mechanisms responsible for suppression of FSH and LH secretion during lactation were investigated in rats, with special reference to the suckling stimulus and ovarian inhibin. Concentrations of immunoreactive inhibin in the peripheral plasma and bioactive inhibin in ovarian venous plasma were always low on days 3 and 5 of lactation in dams nursing eight pups, whereas values were always high on days 17 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups. There was an FSH surge within 48 h after removal of litters on days 3 and 5 of lactation in dams nursing eight pups, whereas plasma concentrations of FSH were unchanged within 48 h by removal of litters on days 17 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups. Plasma LH concentrations increased significantly compared with those of control animals within 24 h after removal of the litter on any day of lactation, regardless of the litter size. Plasma FSH levels increased within 6 h after bilateral or unilateral ovariectomy in lactating rats only on the days when plasma concentrations of inhibin were high before ovariectomy, such as day 17 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups, whereas the mean concentrations of plasma LH showed no significant increase within 12 h after bilateral ovariectomy in these lactating rats. Treatment with progesterone or oestradiol-17β after unilateral ovariectomy did not inhibit the increase in plasma FSH levels, while the increase in plasma concentrations of FSH after surgery was completely inhibited by injecting inhibin (porcine follicular fluid). Treatment with steroid hormones inhibited the basal levels of LH in unilateral ovariectomized lactating rats. Plasma FSH concentrations increased sharply within 6 h after a single i.v. injection of anti-inhibin serum on days 10, 15 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups, whereas only a small but significant increase in concentrations of FSH was noted 6 h after the antiserum treatment on day 5 of lactation in dams nursing eight pups. Concentrations of plasma LH were unchanged by treatment with antiserum in lactating rats throughout lactation. These findings indicate that the suckling stimulus, rather than ovarian factors, is mainly responsible for the suppression of FSH as well as LH secretion during the first half of lactation in rats nursing eight pups. On the other hand, during the second half of lactation in rats nursing eight pups and throughout lactation in rats nursing two pups, ovarian inhibin plays a primary role in the suppression of FSH secretion, whereas ovarian steroids act to suppress LH secretion. Journal of Endocrinology (1991) 129, 119–130

Estrogen inhibition of LH and FSH secretion: effects of a GnRH antagonist

1986 ◽  
Vol 250 (4) ◽  
pp. E341-E345
Author(s):  
M. C. Charlesworth ◽  
N. B. Schwartz
Keyword(s):  
Luteinizing Hormone ◽  
Negative Feedback ◽  
Gnrh Antagonist ◽  
Follicle Stimulating Hormone ◽  
Estradiol Benzoate ◽  
Gonadotropin Releasing Hormone ◽  
Ovariectomized Rats ◽  
Inhibitory Effects ◽  
Dependent Component ◽  
Lh Secretion

Follicle-stimulating hormone (FSH) levels are not suppressed as rapidly or to the same degree as luteinizing hormone (LH) levels in ovariectomized rats treated with either gonadotropin-releasing hormone (GnRH) antagonist or estrogen. The acute inhibitory effects of various doses of estrogen on FSH and LH secretion were examined in cannulated, 2-wk ovariectomized rats. No dose of 17 beta-estradiol, up to 2,500 ng injected intravenously, suppressed FSH, although LH secretion was inhibited 50% within 1 h by 100 ng. In another experiment, estradiol benzoate (EB; 10 or 250 micrograms; sc injection in oil) was only marginally effective in suppressing FSH, compared with LH, levels in serum. Treatment with EB 24 h before or after a 500 micrograms dose of a GnRH antagonist did not reduce LH or FSH to levels lower than those achieved with antagonist alone. These results indicate that the GnRH-dependent component of FSH release and the GnRH-independent component that is unmasked in the presence of GnRH antagonist are sensitive to negative feedback by estrogen, indicating that this steroid is not the primary inhibitory ovarian factor regulating FSH in the rat.

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