Direct effects of free and conjugated steroids on GnRH stimulated LH release in cultured equine anterior pituitary cells.
Abstract: Enzymatically dispersed anterior pituitary cells from donor mares were cultured for 48 h in alpha-modified Eagles' medium containing 10% steroid-free horse serum. The cells were then incubated for 24 h in fresh medium oestrogen followed by a 4-h incubation with or without GnRH. Media and cell extracts were analyzed for LH by radioimmunoassay. In the first series of experiments, pituitary cells from Day-3 dioestrous mares were preincubated with ethanol (control) or different concentrations of E2 (10(-11) to 10(-7) M) for 24 h prior to a 4-h incubation without (basal) or with 1.0 nM GnRH. E2 increased (P less than 0.001) GnRH-stimulated LH release with a maximal response obtained at 10(-10) M E2 with an ED50 of 3 x 10(-11) M E2. Also E2 enhanced greatly the responsiveness of the pituitary to varying concentrations of GnRH by decreasing the minimum effective dose and ED50 by 93% and 78%, respectively, and by increasing the maximum response to GnRH by 250%. E2 had no effect on basal LH secretion. In a second experiment, the effects of E2, E1 and E1S on basal and GnRH stimulated LH release were evaluated. Although E1 increased GnRH-stimulated LH release, the maximally effective dose of E1 to enhance LH release and the ED50 for E1 were 100 times greater than those found for E2. E1S had no oestrogenic activity even at concentrations as high as 100 nM.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1991-01-01 PubMed ID: 1665515
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research study investigates the direct impact of free and conjugated steroids on the release of Luteinizing Hormone (LH) stimulated by Gonadotropin Releasing Hormone (GnRH) in cultured cells from the anterior part of the pituitary gland in horses.
Research Overview
- The study uses anterior pituitary cells from donor mares that were cultured using a specific medium and hormone-free horse serum.
- The cells were then treated with various concentrations of estrogen and incubated with or without GnRH.
- The media and cell extracts were then assessed for LH using a radioimmunoassay technique.
First Series of Experiments
- In the first set of experiments, pituitary cells were premixed with ethanol or varying concentrations of Estradiol (E2) before a 4-hour incubation period either with or without introducing GnRH.
- It was observed that E2 significantly enhanced the release of LH when prompted by GnRH, with the most powerful response observed at a specific concentration of E2.
- Furthermore, E2 dramatically boosted the pituitary’s reaction to varying concentrations of GnRH, reducing the minimum effective dose and augmenting the maximum response to GnRH.
- Interestingly, E2 had no effect on basal LH release.
Second Experiment
- In the second trial, the researchers evaluated the effects of multiple forms of estrogen – E2, Estrone (E1) and Estrone Sulfate (E1S) – on the basic and GnRH-incited LH discharge.
- While E1 increased GnRH-induced LH release, its maximum effective dose and ED50 were 100 times higher than what was observed for E2.
- Notably, E1S showed no estrogenic activity, even at concentrations as high as 100 nM.
In conclusion, this study provides insights into the role of different forms of estrogen in the stimulation of LH release by GnRH in equine anterior pituitary cells. This could potentially highlight key aspects in understanding how variations in hormone levels could affect this hormonal axis in horses.
Cite This Article
APA
Baldwin DM, Roser JF, Muyan M, Lasley B, Dybdal N.
(1991).
Direct effects of free and conjugated steroids on GnRH stimulated LH release in cultured equine anterior pituitary cells.
J Reprod Fertil Suppl, 44, 327-332.
Publication
Researcher Affiliations
- Department of Veterinary Medical Reproduction, University of California, Davis 95616.
MeSH Terms
- Animals
- Cells, Cultured / drug effects
- Estradiol / pharmacology
- Estrogens / pharmacology
- Estrogens, Conjugated (USP) / pharmacology
- Female
- Gonadotropin-Releasing Hormone / physiology
- Gonadotropins, Equine / metabolism
- Horses / physiology
- Luteinizing Hormone / metabolism
- Pituitary Gland, Anterior / drug effects
- Pituitary Gland, Anterior / metabolism
Citations
This article has been cited 1 times.- Kotitschke A, Sadie-Van Gijsen H, Avenant C, Fernandes S, Hapgood JP. Genomic and nongenomic cross talk between the gonadotropin-releasing hormone receptor and glucocorticoid receptor signaling pathways. Mol Endocrinol 2009 Nov;23(11):1726-45.
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