J Korean Soc Pediatr Endocrinol.  2009 Dec;14(2):146-153.

Study on the Reciprocal Interactions between Growth Hormone and Ghrelin in the Rat

• Lee SY
• Shin CH
• Yang SW

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.

Keyword

Ghrelin; Growth hormone; Growth hormone releasing hormone

MeSH Terms

Adult
Animals
Fasting
Ghrelin
Growth Hormone
Growth Hormone-Releasing Hormone
Humans
Male
Plasma
Rats
Rats, Sprague-Dawley
RNA, Messenger
Stomach
Ghrelin
Growth Hormone
Growth Hormone-Releasing Hormone
RNA, Messenger