Hypophysial Responses to Continuous and Intermittent Delivery of Hypothalamic Gonadotropin-Releasing Hormone

Belchetz, P. E.; Plant, Tony M.; Nakai, Yoshikatsu; Keogh, E.J.; Knobil, E.

doi:10.1097/00000658-197904000-00019

Cited by 138 publications

(141 citation statements)

References 0 publications

Supporting

Mentioning

133

Contrasting

Unclassified

Order By: Relevance

“…These observations may be explained by down-regulation of the pituitary GnRH receptors due to continuous GnRH stimulation [45]. The high GnRH secretion associated with MPA treatment postulated in the previous paragraph may therefore have resulted in desensitization of the response of the gonadotropes to GnRH.…”

Section: Discussionmentioning

confidence: 91%

Adenohypophyseal function in bitches treated with medroxyprogesterone acetate

Beijerink

Bhatti

Okkens

et al. 2007

Domestic Animal Endocrinology

View full text Add to dashboard Cite

The aim of this study was to investigate the effects of treatment with medroxyprogesterone acetate (MPA) on canine adenohypophyseal function. Five Beagle bitches were treated with MPA (10 mg/kg, every 4 weeks) and their adenohypophyseal function was assessed in a combined adenohypophyseal function test. Four hypophysiotropic hormones (CRH, GHRH, GnRH, and TRH) were administered before and 2, 5, 8, and 11 months after the start of MPA treatment, and blood samples for determination of the plasma concentrations of ACTH, cortisol, GH, IGF-1, LH, FSH, prolactin, ␣-MSH, and TSH were collected at −15, 0, 5, 10, 20, 30, and 45 min after suprapituitary stimulation.MPA successfully prevented the occurrence of estrus, ovulation, and a subsequent luteal phase. MPA treatment did not affect basal and GnRH-induced plasma LH concentrations. The basal plasma FSH concentration was significantly higher at 2 months after the start of MPA treatment than before or at 5, 8, and 11 months after the start of treatment. The maximal FSH increment and the AUC for N.J. Beijerink et al. / Domestic Animal Endocrinology xxx (2006) xxx-xxxmonths of MPA treatment. Differences in mean basal plasma GH concentrations before and during treatment were not significant, but MPA treatment resulted in significantly elevated basal plasma IGF-1 concentrations at 8 and 11 months. MPA treatment did not affect basal and stimulated plasma ACTH concentrations, with the exception of a decreased AUC for ACTH at 11 months. In contrast, the maximal cortisol increment and the AUC for cortisol after suprapituitary stimulation were significantly lower during MPA treatment than prior to treatment. MPA treatment did not affect basal plasma concentrations of prolactin, TSH, and ␣-MSH, with the exception of slightly increased basal plasma TSH concentrations at 8 months of treatment. MPA treatment did not affect TRH-induced plasma concentrations of prolactin and TSH.In conclusion, the effects of chronic MPA treatment on adenohypophyseal function included increased FSH secretion, unaffected LH secretion, activation of the mammary GH-induced IGF-I secretion, slightly activated TSH secretion, suppression of the hypothalamic-pituitary-adrenocortical axis, and unaffected secretion of prolactin and ␣-MSH.

show abstract

Section: Discussionmentioning

confidence: 91%

Adenohypophyseal function in bitches treated with medroxyprogesterone acetate

Beijerink

Bhatti

Okkens

et al. 2007

Domestic Animal Endocrinology

View full text Add to dashboard Cite

show abstract

“…The remainder affect shape, as four involve the gain or loss of a Cys, one involves Pro, and two are large truncations or deletions (Janovick et al, 2006). These results and the observation that pituitary signaling seems to depend on the pattern of exposure to ligand (Belchetz et al, 1978;Knobil et al, 1980) present the concern that moving this therapeutic approach in vivo, would require some attention to the timing of the administration of the pharmacoperone.…”

Section: E Receptor Concentration At the Plasma Membrane As A Gain Cmentioning

confidence: 99%

“…These enter the peripheral circulation and regulate gonadal steroidogenesis, along with maturation of eggs and sperm. Intermittent exposure of the GnRHR to the releasing hormone is important from a functional point of view; slower GnRH pulses favor release of FSH whereas faster pulses favor release of LH (Belchetz et al, 1978;Crowley et al, 1985;Hazum and Conn, 1988) (Fig. 2).…”

mentioning

confidence: 99%

“…2). Frequency modulated signals are also important to prevent desensitization (refractoriness) of the gonadotrope to a subsequent stimulus, allowing for the occurrence of distinct rates and patterns of synthesis and release of the gonadotropins that follow GnRH exposure (Belchetz et al, 1978). The GnRHR is among the smallest members of the GPCR superfamily (328 amino acid residues in the human GnRHR) and bears unique structural features, including the lack of a carboxyl-terminal intracellular tail (Millar et al, 2004).…”

mentioning

confidence: 99%

See 1 more Smart Citation

G Protein-Coupled Receptor Trafficking in Health and Disease: Lessons Learned to Prepare for Therapeutic Mutant Rescue in Vivo

2007

View full text Add to dashboard Cite

“…GnRH is secreted in pulses and stimulates both LH and FSH synthesis and release [150][151][152][153][154][155][156]. Estrogen from the ovary exerts positive feedback to gonadotropes from diestrus to proestrus and increases the production of GnRH receptors [157] on Fig.…”

Section: Gonadotropin Releasing Hormone (Gnrh)mentioning

confidence: 99%

Pituitary Leptin-A Paracrine Regulator of Gonadotropes: A Review

2011

View full text Add to dashboard Cite

Leptin, a potent anorexigenic hormone secreted primarily by adipocytes, is known to be expressed in the anterior pituitary. Studies in our laboratory found leptin proteins and mRNA predominantly in somatotropes in normal male and cycling female rats. In contrast, leptin expression predominated in gonadotropes during pregnancy and lactation. Leptin expression varied with the cycle and was enhanced, in vitro by gonadotropin releasing hormone and Neuropeptide Y. In contrast, ghrelin inhibited pituitary leptin expression. Pituitary leptin in somatotropes or gonadotropes was reduced by nutritional deprivation for 24 h. However, growth hormone (GH), luteinizing hormone (LH) and pituitary leptin recovered if fasted animals were given glucose water. The glucose-mediated recovery suggests that the system is sensitive to changes in serum glucose. Somatotropes and gonadotropes also recovered if pituitary cells from fasted rats were stimulated in vitro with 1-100 pg/ml leptin. This in vitro leptin-mediated recovery suggests that leptin is important in the maintenance of somaotropes and gonadotropes. Collectively, the data suggest that pituitary leptin might serve as a "glucostat", sensing levels of serum glucose and reporting this nutritional state to somaotropes and gonadotropes in a paracrine manner. A decrease in pituitary leptin might signal nutritional deprivation to somatotropes and gonadotropes, lowering LH and GH production and allowing for conservation of resources. Lower GH would help conserve fat stores and lower LH would promote survival over reproduction.

show abstract

Hypophysial Responses to Continuous and Intermittent Delivery of Hypothalamic Gonadotropin-Releasing Hormone

Cited by 138 publications

References 0 publications

Adenohypophyseal function in bitches treated with medroxyprogesterone acetate

Adenohypophyseal function in bitches treated with medroxyprogesterone acetate

G Protein-Coupled Receptor Trafficking in Health and Disease: Lessons Learned to Prepare for Therapeutic Mutant Rescue in Vivo

Pituitary Leptin-A Paracrine Regulator of Gonadotropes: A Review

Contact Info

Product

Resources

About