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Glucocorticoids regulate pituitary growth hormone secretagogue receptor gene expression
H Tamura1, J Kamegai, H Sugihara
1Department of Medicine, Nippon Medical School, Tokyo, Japan.
Journal of Neuroendocrinology
|June 9, 2000
Summary
Glucocorticoids directly stimulate pituitary growth hormone secretagogue receptor (GHS-R) gene transcription. This regulation is crucial for maintaining normal growth hormone (GH) secretion levels.
Area of Science:
- Endocrinology
- Molecular Biology
- Neuroscience
Background:
- Glucocorticoids influence growth hormone (GH) secretion via hypothalamic and pituitary pathways.
- They are known to upregulate GH and GH-releasing hormone receptor (GHRH-R) gene expression in the pituitary.
Purpose of the Study:
- To investigate whether glucocorticoids regulate the pituitary expression of the growth hormone secretagogue (GHS) receptor (GHS-R).
Main Methods:
- Adult male rats underwent adrenalectomy or sham surgery and received dexamethasone or vehicle treatment.
- Pituitary GHS-R mRNA levels were quantified using reverse transcriptase polymerase chain reaction (RT-PCR).
- Primary rat pituitary cell cultures were used to assess dose- and time-dependent effects and transcriptional regulation.
Main Results:
- Adrenalectomy significantly reduced pituitary GHS-R mRNA levels.
- Dexamethasone administration increased GHS-R mRNA in both sham-operated and adrenalectomized rats.
- Dexamethasone stimulated GHS-R mRNA in pituitary cell cultures, an effect blocked by actinomycin D, indicating transcriptional control.
Conclusions:
- Glucocorticoids directly enhance pituitary GHS-R mRNA levels.
- This effect is mediated by stimulating the transcription of the GHS-R gene.
- These findings highlight a novel regulatory mechanism for GHS-R expression by glucocorticoids.