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Thyroid hormones regulate pituitary growth hormone secretagogue receptor gene expression
1Department of Medicine, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan. jkamegai@nms.ac.jp
Journal of Neuroendocrinology
|February 24, 2001
Summary
Thyroid hormones, like triiodothyronine (T3), boost growth hormone secretagogue receptor (GHS-R) mRNA in pituitary cells. This occurs by increasing the stability of GHS-R mRNA, not by enhancing gene transcription.
Area of Science:
- Endocrinology
- Molecular Biology
- Neuroendocrinology
Background:
- Thyroid hormones influence growth hormone (GH) secretion via hypothalamic and pituitary actions.
- Thyroid hormones elevate GH and GH-releasing hormone receptor (GHRH-R) mRNA expression in the pituitary.
Purpose of the Study:
- To investigate the effect of thyroid hormones on pituitary growth hormone secretagogue receptor (GHS-R) mRNA expression.
- To determine if triiodothyronine (T3) regulates GHS-R mRNA levels in rat pituitary cells.
Main Methods:
- Primary pituitary cell cultures from adult male rats were utilized.
- Cells were treated with triiodothyronine (T3).
- GHS-R mRNA levels were quantified using reverse transcriptase-polymerase chain reaction (RT-PCR).
Main Results:
- T3 treatment significantly increased pituitary GHS-R mRNA levels in a dose- and time-dependent manner.
- The stimulatory effect of T3 on GHS-R mRNA was observed even with actinomycin D, an RNA synthesis inhibitor.
- T3 extended the half-life of GHS-R mRNA from 8 to 15 hours, indicating increased message stability.
Conclusions:
- Thyroid hormones increase pituitary GHS-R mRNA levels.
- This regulation is primarily mediated by enhancing GHS-R mRNA stability rather than by increasing gene transcription.
- Findings elucidate a novel mechanism of thyroid hormone action on pituitary gene expression relevant to GH regulation.