Home  About us  Contact
 

GnRH Antagonist (gnrh + antagonist)

Distribution by Scientific Domains
Medical Sciences62%

Selected Abstracts

Effect of Suppression of FSH with a GnRH Antagonist (Acyline) Before and During Follicle Deviation in the Mare

REPRODUCTION IN DOMESTIC ANIMALS, Issue 3 2009
CM Checura
Contents A GnRH antagonist (Acyline) was used to study the role of FSH in early development of a follicular wave in 61 mares. In Experiment 1, a single dose of 3 mg per mare, compared with 0 and 1 mg, suppressed both the FSH and follicle responses to exogenous GnRH. In Experiment 2, high concentrations of FSH were induced by two successive ablations of all follicles , 6 mm on days 10 and 13 (day 0 = ovulation). A single treatment with Acyline resulted in significantly greater suppression of plasma concentrations of FSH than a single treatment with charcoal-extracted follicular fluid (source of inhibin) or oestradiol. Suppression of FSH was not significantly different between the group treated with Acyline alone and a group treated with a combination of Acyline, inhibin and oestradiol. In Experiment 3, all follicles were ablated on day 10 to induce an FSH surge and a new follicular wave. Acyline treatment on day 10 resulted in an immediate decrease in FSH, without a significant effect on day of emergence of a new wave or growth of follicles from 7 to 11 mm on days 11,13. Treatment on day 15, a day before expected follicle deviation and after the peak of the wave-stimulating FSH surge, resulted in an immediate decrease in FSH and cessation of follicle growth. Results indicated that growth of follicles for about 2 days after wave emergence was independent of FSH. In contrast, during the decline in the wave-stimulating FSH surge and before follicle deviation, growth of follicles was dependent on FSH. [source]

Efficient Synthesis of Bicyclic Oxazolino- and Thiazolino[3,2-c]pyrimidine-5,7-diones and Its Application to the Synthesis of GnRH Antagonists.

CHEMINFORM, Issue 28 2005
Joseph Pontillo
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

KiSS-1 and GPR54 Genes are Co-Expressed in Rat Gonadotrophs and Differentially Regulated In Vivo by Oestradiol and Gonadotrophin-Releasing Hormone

JOURNAL OF NEUROENDOCRINOLOGY, Issue 3 2008
N. Richard
Kisspeptin, the product derived from KiSS-1, and its cognate receptor, GPR54, both exert a role in the neuroendocrine control of reproduction by regulating gonadotrophin-releasing hormone (GnRH) secretion. In the present study, we demonstrate, using dual immunofluorescence with specific antibodies, that the KiSS-1 and GPR54 genes are both expressed in rat gonadotrophs. All luteinising hormone ,-immunoreactive (LH,-ir) cells were stained by the KiSS-1 antibody but some kisspeptin-ir cells were not LH, positive; thus, we cannot exclude the possibility that kisspeptins are expressed in other pituitary cells. All GPR54-ir are co-localised with LH, cells, but only a subset of LH, cells are stained with the GPR54 antibody. Using the real-time reverse transcription-polymerase chain reaction (RT-PCR), we found that the expression of KiSS-1 and GPR54 is differentially regulated by steroids. In the female, KiSS-1 mRNA levels dramatically decreased following ovariectomy (OVX), and this decrease was prevented by administration of 17,-oestradiol (E2), but not by administration of GnRH antagonist or agonist. Administration of E2 in OVX rats receiving either GnRH antagonist or agonist clearly shows that E2 acts directly on the pituitary to positively control KiSS-1 expression. In OVX rats, administration of the selective oestrogen receptor (ER), ligand propylpyrazoletriol, but not the selective ER, ligand diarylpropionitrile, mimics this effect. By contrast, our study shows that GPR54 expression is positively regulated by GnRH and negatively controlled by chronic exposure to E2. In summary, our data document for the first time that, in the female rat pituitary, KiSS-1 expression is up-regulated by oestradiol, similarly to that seen in the anteroventral periventricular nucleus of the hypothalamus. Conversely, GPR54 is up-regulated by GnRH, which exclusively targets gonadotrophs. [source]

Effect of Suppression of FSH with a GnRH Antagonist (Acyline) Before and During Follicle Deviation in the Mare

REPRODUCTION IN DOMESTIC ANIMALS, Issue 3 2009
CM Checura
Contents A GnRH antagonist (Acyline) was used to study the role of FSH in early development of a follicular wave in 61 mares. In Experiment 1, a single dose of 3 mg per mare, compared with 0 and 1 mg, suppressed both the FSH and follicle responses to exogenous GnRH. In Experiment 2, high concentrations of FSH were induced by two successive ablations of all follicles , 6 mm on days 10 and 13 (day 0 = ovulation). A single treatment with Acyline resulted in significantly greater suppression of plasma concentrations of FSH than a single treatment with charcoal-extracted follicular fluid (source of inhibin) or oestradiol. Suppression of FSH was not significantly different between the group treated with Acyline alone and a group treated with a combination of Acyline, inhibin and oestradiol. In Experiment 3, all follicles were ablated on day 10 to induce an FSH surge and a new follicular wave. Acyline treatment on day 10 resulted in an immediate decrease in FSH, without a significant effect on day of emergence of a new wave or growth of follicles from 7 to 11 mm on days 11,13. Treatment on day 15, a day before expected follicle deviation and after the peak of the wave-stimulating FSH surge, resulted in an immediate decrease in FSH and cessation of follicle growth. Results indicated that growth of follicles for about 2 days after wave emergence was independent of FSH. In contrast, during the decline in the wave-stimulating FSH surge and before follicle deviation, growth of follicles was dependent on FSH. [source]

Abarelix and other gonadotrophin-releasing hormone antagonists in prostate cancer

BJU INTERNATIONAL, Issue 11 2009
Roger S. Kirby
Hormonal therapy is the main recommended treatment for locally advanced and metastatic prostate cancer. Luteinizing hormone-releasing hormone (LHRH) agonists, such as buserelin, goserelin, leuprorelin and triptorelin, stimulate the pituitary's gonadotrophin-releasing hormone (GnRH) receptor, ultimately leading to its de-sensitization and subsequent reduction of LH and testosterone levels. However, this reduction is accompanied by a well described increase or ,surge' in LH and testosterone levels, necessitating the concomitant administration of an antiandrogen to combat the potential effects of transient acceleration in cancer activity. Two pure GnRH antagonists have been developed, abarelix and degarelix, that are devoid of any agonist effect on the GnRH receptor and consequently do not result in testosterone flare. Abarelix was the first GnRH antagonist to be developed and was approved by the USA Food and Drug Administration in 2004 for the initiation of hormonal castration in advanced or metastasizing hormone-dependent prostate carcinoma, when rapid androgen suppression is necessary. Clinical data on both abarelix and degarelix show that they can produce rapid and sustained decreases in testosterone to castrate levels without the need for co-administration of an antiandrogen, and with a very low complication rate in the short term. [source]

Synthesis and biological activity of GnRH antagonists modified at position 3 with 3-(2-methoxy-5-pyridyl)-alanine,

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 2 2005
M.P. Samant
Abstract:, Degarelix is a potent very long-acting GnRH antagonist after subcutaneous administration. In this paper, we describe the synthesis of two analogs of degarelix incorporating racemic 3-(2-methoxy-5-pyridyl)-alanine (2-OMe-5Pal, 5) at position 3. The two diastereomers were separated by reverse-phase high-performance liquid chromatography (RP-HPLC) and the absolute stereochemistry at position 3 in the peptides was determined by enzymatic digestion with proteinase K. These analogs were tested in vitro for their ability to antagonize the GnRH receptor and in vivo for duration of action in a castrated male rat assay. Analog 7 with D2-OMe-5Pal was potent in vitro (IC50 = 5.22 nm); however, analog 8 with L2-OMe-5Pal at position 3 in degarelix lost potency as an antagonist of the human GnRH receptor (IC50 = 36.95 nm). Both the analogs were found to be short-acting in vivo. [source]

Abarelix and other gonadotrophin-releasing hormone antagonists in prostate cancer

BJU INTERNATIONAL, Issue 11 2009
Roger S. Kirby
Hormonal therapy is the main recommended treatment for locally advanced and metastatic prostate cancer. Luteinizing hormone-releasing hormone (LHRH) agonists, such as buserelin, goserelin, leuprorelin and triptorelin, stimulate the pituitary's gonadotrophin-releasing hormone (GnRH) receptor, ultimately leading to its de-sensitization and subsequent reduction of LH and testosterone levels. However, this reduction is accompanied by a well described increase or ,surge' in LH and testosterone levels, necessitating the concomitant administration of an antiandrogen to combat the potential effects of transient acceleration in cancer activity. Two pure GnRH antagonists have been developed, abarelix and degarelix, that are devoid of any agonist effect on the GnRH receptor and consequently do not result in testosterone flare. Abarelix was the first GnRH antagonist to be developed and was approved by the USA Food and Drug Administration in 2004 for the initiation of hormonal castration in advanced or metastasizing hormone-dependent prostate carcinoma, when rapid androgen suppression is necessary. Clinical data on both abarelix and degarelix show that they can produce rapid and sustained decreases in testosterone to castrate levels without the need for co-administration of an antiandrogen, and with a very low complication rate in the short term. [source]

Synthesis and biological activity of GnRH antagonists modified at position 3 with 3-(2-methoxy-5-pyridyl)-alanine,

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 2 2005
M.P. Samant
Abstract:, Degarelix is a potent very long-acting GnRH antagonist after subcutaneous administration. In this paper, we describe the synthesis of two analogs of degarelix incorporating racemic 3-(2-methoxy-5-pyridyl)-alanine (2-OMe-5Pal, 5) at position 3. The two diastereomers were separated by reverse-phase high-performance liquid chromatography (RP-HPLC) and the absolute stereochemistry at position 3 in the peptides was determined by enzymatic digestion with proteinase K. These analogs were tested in vitro for their ability to antagonize the GnRH receptor and in vivo for duration of action in a castrated male rat assay. Analog 7 with D2-OMe-5Pal was potent in vitro (IC50 = 5.22 nm); however, analog 8 with L2-OMe-5Pal at position 3 in degarelix lost potency as an antagonist of the human GnRH receptor (IC50 = 36.95 nm). Both the analogs were found to be short-acting in vivo. [source]