백서에서 성장호르몬과 그렐린의 상호작용에 관한 연구
Study on the Reciprocal Interactions between Growth Hormone and Ghrelin in the Rat
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목 적:본 연구에서 성장호르몬과 그렐린의 상호작용에 의해 서로의 합성과 혈중 농도에 미치는 영향에 대해 살펴보고자 하였다. 방 법:수컷 Sprague-Dawley 쥐(체중 250-300 g)를 대상으로 쥐 그렐린 10 μg 혹은 동량의 생리식염수를 정맥주사한 후 10분 뒤 혈장 성장호르몬 농도를 측정하고 즉시 단두하여 뇌하수체의 성장호르몬 mRNA와 시상하부의 성장호르몬방출호르몬 mRNA의 발현을 측정하였다. 또 식이를 제한하지 않은 군과 금식시킨 군으로 나누어 3일간 사람 성장호르몬 500 μg/kg 또는 동량의 생리식염수를 하루 2번 피하주사 한 후 혈장 그렐린 농도와 위의 그렐린 mRNA의 발현을 측정하였다. 결 과:혈장 성장호르몬은 그렐린을 투여한 군에서 식염수를 투여한 군보다 유의하게 높았다(P˂0.05). 그러나 뇌하수체의 성장호르몬 mRNA와 시상하부의 성장호르몬방출호르몬 mRNA의 발현은 두 군 간에 차이가 없었다. 금식 여부에 관계없이 3일간 성장호르몬을 투여한 군의 혈장 그렐린 농도와 위의 그렐린 mRNA의 발현은 식염수를 투여한 군과 유의한 차이가 없었다. 금식 여부에 따른 비교를 하였을 때, 금식을 시킨 군에서 혈장 그렐린 농도(P˂0.05)와 위의 그렐린 mRNA 발현(P˂0.05)은 유의하게 증가하였고 결 론:그렐린의 투여는 성장호르몬의 분비를 촉진시키나 성장호르몬 및 성장호르몬방출호르몬의 생성을 증가시키지는 않는다. 또 위의 그렐린 생성과 혈장 그렐린 농도는 성장호르몬 투여의 영향을 받지 않아 음성 되먹이기 기전이 존재하지 않는 것으로 보인다.
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 µg 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 μg/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.
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