Micic D, Popovic V, Kendereski A, Macut D, Casanueva F F, Dieguez C
Institute of Endocrinology, University Clinical Center, Belgrade, Yugoslavia.
Clin Endocrinol (Oxf). 1995 Feb;42(2):191-4. doi: 10.1111/j.1365-2265.1995.tb01861.x.
Growth hormone (GH) secretion in middle and late adulthood declines with age. However, the precise mechanisms causing this impairment in GH release are unknown. His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GHRP-6) is a synthetic compound that releases GH in a dose related and specific manner in several species, including man. In order to gain a further insight into disrupted GH secretion in late adulthood, we evaluated GH responses to GHRP-6 or GHRH, administered either alone or in combination, in healthy young and late adulthood groups of subjects.
All subjects underwent three different tests carried out in random order and separated by at least one week. Tests were performed at 0900 h after an overnight fast. GHRH (100 micrograms), GHRP-6 (90 micrograms) either alone or in combination were administered as an i.v. bolus.
Groups of healthy young (mean +/- SEM 22 +/- 1.1 years, n = 9) and older adult subjects (59.5 +/- 1.7 years, n = 9) were studied.
Serum GH levels were measured by radioimmunoassay.
In the group of young adult subjects the combined administration of GHRH and GHRP-6 elicited a greater GH increase than GHRH alone (F = 21.9, P < 0.001) or GHRP-6 alone (F = 6.2, P = 0.01). Similarly, the response to the combined stimuli was also greater than with GHRH alone (F = 21.8, P < 0.001) or GHRP-6 alone (F = 23.9, P < 0.001) in the late adulthood group of subjects. GH responses to GHRH were greater in younger than in older subjects (F = 3.45, P = 0.03). In contrast, GH responses to either GHRP-6 (F = 0.71, P = NS) or combined GHRH plus GHRP-6 administration (F = 0.68, P = NS) were not significantly different between the two groups.
These data show that GH responses to GHRP-6 are much greater than to GHRH in late adulthood. The marked increase of plasma GH levels observed after administration of GHRP-6 alone or in combination with GHRH indicates that impaired GH secretion in late adulthood is a functional and potentially reversible state.
在成年中期和后期，生长激素（GH）的分泌会随着年龄增长而下降。然而，导致GH释放受损的确切机制尚不清楚。组氨酸-右旋色氨酸-丙氨酸-右旋色氨酸-右旋苯丙氨酸-赖氨酸-氨基（GHRP-6）是一种合成化合物，在包括人类在内的多个物种中，它能以剂量相关且特异的方式释放GH。为了更深入了解成年后期GH分泌紊乱的情况，我们评估了健康青年组和成年后期组受试者单独或联合给予GHRP-6或生长激素释放激素（GHRH）后的GH反应。
所有受试者以随机顺序接受三项不同测试，且测试间隔至少一周。测试在禁食过夜后的09:00进行。单独或联合给予GHRH（100微克）、GHRP-6（90微克），静脉推注给药。
研究了健康青年组（平均±标准误22±1.1岁，n = 9）和老年成年组受试者（59.5±1.7岁，n = 9）。
通过放射免疫测定法测量血清GH水平。
在青年成年组受试者中，联合给予GHRH和GHRP-6引起的GH升高幅度大于单独给予GHRH（F = 21.9，P < 0.001）或单独给予GHRP-6（F = 6.2，P = 0.01）。同样，在成年后期组受试者中，联合刺激的反应也大于单独给予GHRH（F = 21.8，P < 0.001）或单独给予GHRP-6（F = 23.9，P < 0.001）。青年受试者对GHRH的GH反应大于老年受试者（F = 3.45，P = 0.03）。相比之下，两组之间对GHRP-6（F = 0.71，P = 无显著性差异）或联合给予GHRH加GHRP-6的GH反应（F = 0.68，P = 无显著性差异）无显著差异。
这些数据表明，在成年后期，GH对GHRP-6的反应远大于对GHRH的反应。单独或与GHRH联合给予GHRP-6后观察到的血浆GH水平显著升高表明，成年后期GH分泌受损是一种功能性且可能可逆的状态。
