scholarly journals The pituitary gonadotropin-releasing hormone (GnRH) receptor of the female rabbit: characterization and developmental aspects

1992 ◽  
Vol 70 (12) ◽  
pp. 1639-1646
Author(s):  
E. V. Younglai ◽  
E. C. Todoroff
Keyword(s):  
Luteinizing Hormone ◽  
Binding Site ◽  
Sexual Maturation ◽  
Binding Sites ◽  
Gonadotropin Releasing Hormone ◽  
Adult Rabbit ◽  
Releasing Hormone ◽  
Female Rabbit ◽  
Pituitary Gonadotropin ◽  
Site Number

The aim of the present study was to characterize the pituitary gonadotropin-releasing hormone (GnRH) binding site in the rabbit and investigate its possible role in sexual maturation of the female rabbit. A radioligand binding assay was established, and the presence of specific 125I-labelled D-Ala6-des-Gly10-GnRH ethylamide (125I-DAla6EA) binding sites in the anterior pituitary gland of the rabbit was demonstrated. 125I-DAla6EA binding was saturable, specific, displaceable, reversible, correlated with increasing tissue concentrations, and susceptible to physiological manipulation. 125I-DAla6EA binding indicated the presence of two binding sites in the female adult rabbit pituitary: a high affinity, low capacity site (KD = 0.3–0.4 nM; Bmax = 100–200 fmol/mg protein) and a lower affinity, high capacity site (KD = 30 nM; Bmax = 5–8000 fmol/mg protein). Ontogeny of 125I-DAla6EA binding in the female rabbit (40–120 days of age) did not show a correlation between binding site number and serum luteinizing hormone (LH). In addition, the net serum LH response in female rabbits to a subcutaneous injection of DAla6EA (10 ng, 100 ng, and 1 μg per kilogram body weight) was not significantly different between animals 40, 75, and 120 days of age. This suggests that a decrease in pituitary responsiveness to GnRH is not associated with sexual maturation in the female rabbit. Results indicate that factors other than and (or) in addition to GnRH binding site number, such as postreceptor events, play a role in gonadotropin secretion in the female rabbit.Key words: gonadotropin-releasing hormone, receptors, luteinizing hormone, female rabbit.

Relation of attenuated proestrous luteinizing hormone surges in middle-aged female rats to in vitro pituitary gonadotropin-releasing hormone responsiveness

1994 ◽  
Vol 130 (5) ◽  
pp. 540-544 ◽  
Author(s):  
Aurelia N Brito ◽  
Timothy E Sayles ◽  
Richard J Krieg ◽  
Dennis W Matt
Keyword(s):  
Luteinizing Hormone ◽  
Gonadotropin Releasing Hormone ◽  
Female Rats ◽  
Aged Rats ◽  
Middle Aged ◽  
Releasing Hormone ◽  
Young Females ◽  
Pituitary Gonadotropin ◽  
Hormone Responsiveness

Brito AN, Sayles TE, Krieg Jr RJ, Matt DW. Relation of attenuated proestrous luteinizing hormone surges in middle-aged female rats to in vitro pituitary gonadotropin-releasing hormone responsiveness. Eur J Endocrinol 1994;130:540–4. ISSN 0804–4643 Prior to the cessation of regular cyclicity, middle-aged rats display pre-ovulatory luteinizing hormone (LH) surges of reduced magnitude. The present study was designed to identify whether middle-aged female rats with attenuated proestrous LH surges have alterations in pituitary responsiveness to gonadotropin-releasing hormone (GnRH). Young (4 months old) and middle-aged (10–12 months old) regularly cycling females were catheterized and sampled on proestrus to characterize their LH surge profiles. On the next proestrus (12.00 h), pituitaries were perifused individually and exposed to three pulses of GnRH (30 nmol/l). The patterns of the proestrous LH surges revealed that 12 of 22 middle-aged rats had attenuated surges (< 7 μg/l) while the remaining 10 middle-aged females had surges that were similar to those of young rats. Pituitaries perifused on the next proestrus showed similar basal LH release among the middle-aged and young females. However, the LH secretory rates following the second and third administration of GnRH, as well as the overall GnRH-stimulated LH secretory rates, were significantly decreased in middle-aged females with previously attenuated LH surges as compared to those from the young proestrous rats. In contrast, middle-aged rats with normal LH surges had pituitary LH responses that were no different from those of young females. These results indicate that a decrease in pituitary LH responsiveness to GnRH is only apparent in middle-aged rats that display attenuated proestrous LH surges. Dennis W Matt. Department of Obstetrics and Gynecology, Medical College of Virginia, Box 980034, Richmond, VA 23298, USA

Pituitary and gonadal responsiveness is enhanced during GnRH-induced puberty

1988 ◽  
Vol 254 (5) ◽  
pp. E652-E657
Author(s):  
D. I. Spratt ◽  
W. F. Crowley
Keyword(s):  
Luteinizing Hormone ◽  
Sexual Maturation ◽  
Sexual Development ◽  
Follicle Stimulating Hormone ◽  
Gonadotropin Releasing Hormone ◽  
Releasing Hormone ◽  
Hormone Levels ◽  
Gnrh Secretion ◽  
Serum Luteinizing Hormone ◽  
Before And After

We hypothesized that the hypothalamic gonadotropin-releasing hormone (GnRH) signal that initiates sexual maturation is further amplified at both the pituitary and gonadal levels during puberty. To test this theory, six GnRH-deficient men were monitored during administration of exogenous GnRH at a physiological frequency for greater than or equal to 9 mo. GnRH doses were progressively increased until normal testosterone (T) concentrations and secondary sexual development were achieved. This "optimized" dose of GnRH was then sustained for at least 6 mo to allow maturation of the hypothalamic-pituitary-gonadal axis. The GnRH dose was then progressively decreased to a level that had been unable to stimulate normal T secretion before sexual maturation. Changes in pituitary responsiveness were analyzed in four of the six men by comparing gonadotropin responses to identical doses of GnRH before and after sexual maturation. Mean serum luteinizing hormone and follicle-stimulating hormone levels as well as luteinizing hormone pulse amplitudes were greater after the induction of sexual maturation than before despite identical doses of GnRH. Both pituitary and gonadal responsiveness was then analyzed in the remaining two subjects by choosing periods of evaluation where endogenous gonadotropin levels were matched before and after the period of sexual maturation. Serum T concentrations were greater after sexual maturation than before despite equivalent gonadotropin input to the testes and LH pulse amplitudes. Thus the testicular responsiveness to gonadotropins increased during sexual maturation. After initiation of puberty by GnRH secretion, amplification at both the pituitary and gonadal levels contributes to sexual maturation in the human.

Pituitary Gonadotropin-Releasing Hormone Binding Sites in Persistent Estrous Rats

1988 ◽  
Vol 48 (5) ◽  
pp. 489-494 ◽  
Author(s):  
Katalin Köves ◽  
Bernard Kerdelhué ◽  
Judith Molnár ◽  
Valér Csernus ◽  
Béla Halász
Keyword(s):  
Binding Sites ◽  
Gonadotropin Releasing Hormone ◽  
Hormone Binding ◽  
Releasing Hormone ◽  
Pituitary Gonadotropin

Gonadal Regulation of Pituitary Gonadotropin-Releasing Hormone Receptors during Sexual Maturation in the Rat*

Endocrinology ◽  
1983 ◽  
Vol 113 (6) ◽  
pp. 2238-2246 ◽  
Author(s):  
JOYCE A. DUNCAN ◽  
ALAN C. DALKIN ◽  
ARIEL BARKAN ◽  
SANDRA REGIANI ◽  
JOHN C. MARSHALL
Keyword(s):  
Sexual Maturation ◽  
Hormone Receptors ◽  
Gonadotropin Releasing Hormone ◽  
Releasing Hormone ◽  
Pituitary Gonadotropin

scholarly journals Regulation of gonadotropin subunit gene transcription

2004 ◽  
Vol 33 (3) ◽  
pp. 559-584 ◽  
Author(s):  
L L Burger ◽  
D J Haisenleder ◽  
A C Dalkin ◽  
J C Marshall
Keyword(s):  
Transcriptional Regulation ◽  
Luteinizing Hormone ◽  
Gene Transcription ◽  
Sexual Maturation ◽  
Follicle Stimulating Hormone ◽  
Reproductive Function ◽  
Gonadotropin Releasing Hormone ◽  
Subunit Gene ◽  
Pulsatile Release ◽  
Releasing Hormone

Reproductive function in mammals is regulated by the pituitary gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH are secreted by the gonadotrope cell and act on the gonad in a sequential and synergistic manner to initiate sexual maturation and maintain cyclic reproductive function. The synthesis and secretion of LH and FSH are regulated mainly by the pulsatile release of the hypothalamic decapeptide hormone gonadotropin-releasing hormone (GnRH). The control of differential LH and FSH synthesis and secretion is complex and involves the interplay between the gonads, hypothalamus and pituitary. In this review, the transcriptional regulation of the gonadotropin subunit genes is discussed in a physiologic setting, and we aimed to examine the mechanisms that drive those changes.

Sign in / Sign up

Export Citation Format

Share Document