Massoud A F, Hindmarsh P C, Brook C G
London Centre for Paediatric Endocrinology and Metabolism, Middlesex Hospital, UK.
Clin Endocrinol (Oxf). 1995 Nov;43(5):617-21. doi: 10.1111/j.1365-2265.1995.tb02927.x.
Growth hormone releasing peptides (GHRPs) are a group of synthetic compounds capable of releasing GH by an unknown mechanism. The aim of this study was to determine the effect of administering biosynthetic human growth hormone (rhGH) on the GH releasing activity of hexarelin, a new and potent GHRP, and to compare the results with those obtained with growth hormone releasing hormone (GHRH).
Boluses of saline or rhGH were administered intravenously, followed 90 minutes later by a second intravenous bolus of saline, hexarelin or GHRH. Studies were performed following an overnight fast. Each subject underwent six studies performed in a random order and separated by at least 2 days.
Six healthy adult males (23.8-34.3 years) were studied.
Serum GH and IGF-I levels were measured by radioimmunoassay.
The peak serum GH response to hexarelin was greater than that to GHRH, irrespective of whether the first bolus was saline (P < 0.05) or rhGH (P < 0.02). Prior administration of rhGH led to a reduction in peak serum GH response to hexarelin or GHRH (P < 0.05); the percentage reduction in response to hexarelin was less than that to GHRH, but this difference was not statistically significant (P = 0.3). There was no change in serum IGF-I concentration before or 90 minutes after the administration of rhGH.
Hexarelin is a potent GH secretagogue subject to partial feedback inhibition by rhGH. This raises issues about its mechanism of action and may have implications for its potential therapeutic use.
生长激素释放肽（GHRPs）是一类能够通过未知机制释放生长激素（GH）的合成化合物。本研究的目的是确定给予生物合成的人生长激素（rhGH）对一种新型强效GHRP——六肽生长激素释放肽（hexarelin）的GH释放活性的影响，并将结果与生长激素释放激素（GHRH）的结果进行比较。
静脉注射生理盐水或rhGH推注，90分钟后再静脉注射生理盐水、六肽生长激素释放肽或GHRH推注。研究在过夜禁食后进行。每位受试者按随机顺序进行六项研究，且研究间隔至少2天。
研究了6名健康成年男性（23.8 - 34.3岁）。
采用放射免疫分析法测定血清GH和IGF - I水平。
无论首次推注是生理盐水（P < 0.05）还是rhGH（P < 0.02），六肽生长激素释放肽引起的血清GH峰值反应均大于GHRH引起的反应。预先给予rhGH导致血清GH对六肽生长激素释放肽或GHRH的峰值反应降低（P < 0.05）；对六肽生长激素释放肽反应的降低百分比小于对GHRH反应的降低百分比，但这种差异无统计学意义（P = 0.3）。给予rhGH前后90分钟血清IGF - I浓度无变化。
六肽生长激素释放肽是一种强效的GH促分泌剂，受到rhGH的部分反馈抑制。这引发了关于其作用机制的问题，可能对其潜在的治疗用途有影响。
