Regulational Effect of Ghrelin on Growth Hormone Secretion from Perifused Rat Anterior Pituitary Cells

Journal of Neuroendocrinology - Tập 14 Số 2 - Trang 156-162 - 2002
Mami Yamazaki1, Kazuaki Nakamura1, Haruo Kobayashi2, Maki Matsubara1, Yoshitaka Hayashi3, Kenji Kangawa4, Tatsuo Sakai1
1Department of Regulation Biology, Faculty of Science, Saitama University, Shimo‐ohkubo, Saitama, Saitama, Japan.
2Biosignal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Showa-machi, Maebashi, Gunma, Japan.
3Suntory Institute of Medicine Research Development, Akaiwa, Chiyoda, Gunma, Japan.
4Department of Biochemistry, National Cardiovascular Center Research Institute, Fujishirodai, Suita, Osaka, Japan.

Tóm tắt

AbstractGhrelin, a novel growth hormone (GH)‐releasing peptide, was recently isolated from the rat stomach as an endogenous ligand to growth hormone secretagogue receptor (GHS‐R). Ghrelin specifically stimulates the release of GH from the rat anterior pituitary gland, but the regulational effect of ghrelin on GH secretion has not yet been clarified. We used a perifusion system to examine the single effect and combined effects of ghrelin with growth hormone‐releasing hormone (GHRH) and somatostatin on GH secretion from rat anterior pituitary cells. The increase in GH concentration due to ghrelin stimulation showed a transitory peak that was almost the same as that previously reported for GHS, but apparently distinct from that of GHRH. Ghrelin (10−10 M to 10−8 M) stimulated GH secretion from the rat anterior pituitary cells in a dose‐dependent manner. Serial ghrelin stimulation of the dispersed cells at 1‐h intervals decreased the GH response, but the response recovered with stimulation at 3‐h intervals, indicating that ghrelin strongly desensitized cells. Costimulation with ghrelin and GHRH elicited neither a synergistic nor an additive GH response from the rat pituitary cells. Furthermore, pretreatment to anterior pituitary cells with somatostatin strongly abolished ghrelin‐ and/or GHRH‐stimulated GH secretion. In this study, we demonstrated that ghrelin caused weaker GH secretion than that caused by GHRH, and we also showed that costimulation with GHRH had no additive or synergistic effect on GH secretion, suggesting that ghrelin indirectly affects coordinated GH release from pituitary gland, as found in vivo.

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Thông tin xuất bản

Journal of Neuroendocrinology

Tập 14 Số 2

156-162

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