| Study on the Reciprocal Interactions between Growth Hormone and Ghrelin in the Rat. |
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Seong Yong Lee, Choong Ho Shin, Sei Won Yang |
1Department of Pediatrics, Seoul Metropolitan Boramae Medical Center, Korea.
2Department of Pediatrics, College of Medicine, Seoul National University, Seoul, Korea. chshinpd@snu.ac.kr |
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| Abstract |
PURPOSE
The aim of this study was to determine whether there is a feedback relationship between pituitary growth hormone (GH) and gastric ghrelin.
METHODS: We intravenously administered 10 microgram of either rat ghrelin or normal saline to adult male Sprague-Dawley rats and then measured the plasma GH levels and the mRNA expression levels of pituitary GH mRNA and hypothalamic GH-releasing hormone (GHRH) mRNA. Human GH (500 microgram/kg, twice a day) or normal saline was subcutaneously administered to rats with or without food for 3 days. Thereafter, the plasma ghrelin levels and the ghrelin mRNA levels in the stomach were measured.
RESULTS
The plasma GH levels increased more significantly in rats that were administered ghrelin than in controls (P<0.05). The mRNA levels of pituitary GH and hypothalamic GHRH were similar in the 2 groups. The plasma ghrelin levels and the stomach ghrelin mRNA levels were not affected by GH administration. Fasting significantly increased plasma ghrelin levels (P<0.05) and stomach ghrelin mRNA levels (P<0.05).
CONCLUSION
Exogenous ghrelin administration only stimulated GH secretion without stimulating the synthesis of GH and GHRH. The synthesis and secretion of ghrelin were not suppressed by exogenous GH administration. These findings indicate that there is no feedback relationship between pituitary GH and gastric ghrelin. |
| Keywords:
Ghrelin;Growth hormone;Growth hormone releasing hormone |
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